Are you sure its not there, screwed flat onto the bottom of the unit? Thats what they do with the heat shield on induction cooktops and you have to remove it and screw it back on so that it projects out.

The requirement makes perfect sense for a range and zero sense for a rangetop. A range will be belching out searing hot gases from the vent; some of those gases may be drawn back down behind the range because the oven burner is drawing air in. So those hot gases might scorch the area just behind and below the vent. Obviously none of that applies to the rangetop. Before anyone pipes up with fanciful theories about the back of the rangetop becoming hot enough to scorch anything: if that were the case the stipulation would apply regardless of which style of trim you are using, and would also apply to the sides. You are right Bluestar seems very focused on the range and the rangetop is just an afterthought - a range sold without the oven below it. They don't seem to do anything special to support the rangetop in their documentation. For example, when we opened the box our rangetop came in, the first thing on top was a single sheet with some caution about unpacking regarding the range door. That made no sense to put in a box with just a range top - there was no door, but it was there. I guess they just did their normal packing the same regardless of whether it was a big box for a range or a flatter box for a rangetop. However, I don't entirely understand your reasoning above. I can see that hot air from the oven may vent out the vent. But why would the oven burner the exhaust down the back of the range? I doubt that the air intake is on the back of the range which would be against a wall. If it was, a grease fire in the oven might send heat directly out that way and be a fire hazard. Also, if your explanation is correct, why wouldn't that also be a potential problem with the taller vents? The regular back is about 6" higher so any gases in the vent won't have cooled very much by the time they get to the top of it and if there is something that can suck the vented air behind the island vent, why wouldn't that same suction suck air behind the regular back vent? But I agree that it is difficult to see a scenario where the rangetop without the oven below needs a non-combustible surface behind it below the height of the rangetop. The island vent (and probably the same is true for the other two backs) has an internal divider in it. The front of the vent connects to the area under the rangetop burners and the back would connect to the oven if it was a full range and is just open to the cabinet below when there is no range. In normal operation, convection will pull air from that space below the burner past the burner and the oxygen in that air will feed the combustion with the hot air flowing under the pot and up. Replacement air will be pulled in the through the island vent (or the other backs) and through any burners not currently running. So the air going through the island vent for the burners would be cool intake air, not hot exhaust gases. Perhaps if there was an accident such as grease spilling into the area below the burners and igniting there could be hot exhaust air coming up part of the vent and the back could get hot - but why would the island back get hotter than the regular back in that case? Anyway, that's why I was okay with our contractor's recommendation of putting a metal flashing on the cabinets behind the rangetop. That's a fairly minimal non-combustible barrier, but there is also the back of the vent, the air gap for the unused oven vent and a metal separator isolating the cabinet back from the rangetop burner vent area.

Thanks so much for your responses! Yes, the cutouts were all done by the stone company. Also, Kitchenaid does NOT recommend supports under their cook tops. We spoke with someone from the company specifically to have that information in case they tried to blame that. I actually helped install the hood, with the homeowner. At no time did we stand on or apply full weight on the counter top or it's edge. I also did the tile work, and took extreme care to not lean on the edges, for fear of possible scratching of the stone (it's much softer than my own soapstone). We installed the hood several months ago also, and this kitchen has just now showed the cracks within this past month. The 36 inch cabinet from Ikea does not appear to be level on it's front edge and appears to have dropped a bit in it's center. Not sure if the two drawers in this cabinet have been overloaded, although the drawers function just fine. The person representing the Ikea installer, thinks this cabinet's front is pretty normal, and she's never seen stone do this before 'in similar installations.' The soapstone installer never checked for level since 'that is only done at templating' and they 'don't check for level again after that,' according to the rep from the stone company. The initial rep for the stone install company actually accused the homeowner of jumping on the counter since 'that is the only way this could have happened.' At no time has it been suggested by either company's reps to reinforce this 3 cm stone. When we suggested it, they said, 'well, we could' once it's epoxied. But, they really weren't sure since they've 'never seen this problem before.' Btw, all the above quotes were actual things heard while the reps were trying to figure out what to do. I can't believe this has never happened anywhere! Anyone else out there with suggestions or thoughts? And thanks again so very much.

Due to the morass of electronics used with the induction type cooktop, and the need for heat sinks and air ducts for cooling the drive transistors, the induction cooktop would be expected to require more volume below the counter. You would need to measure your radiant cooktop and compare to the dimensions for the Frigidaire cooktop. "Some assembly required." It is likely that you will either have to replace the brackets, modify the brackets, adapt new brackets to old brackets, or perform some other DIY project solution. Keep in mind this is the duct-tape part of a belt, suspenders, and duct-tape safety system. You only need to find a way to keep the unit in the hole in case of earthquake, keep it from sliding around, and keep it from falling down if all the Ceran breaks. However, if Code Enforcement is involved, a satisfactory solution depends on his opinion. (Did you determine that the Frigidaire cutout equals the GE cutout? The Electrolux brands' cutouts are among the largest of those needed for induction cooktops -- at least at the 36-inch size. You may have to have some granite cut, or a "frame" built, depending on match or mismatch.)