I have whisper warm and we installed a timer switch for the fan portion so we dont have to remember to turn the fan off when we are leaving the bathroom. Works great. I was told it cant go inside the shower though so ours is right outside where you step out and the heater is great. I too bought one bigger than the space called for and have no regrets. I read that some complained that the heater didnt warm up enough and that made me get the larger size. The heater is great! Remember though that it takes a whole circuit breaker of its own-20 amp if I recall correctly so make sure you have enough space on your electric box.

Think you missed something, Tom. She doesn't want to vent into the attic. She wants to vent OUTSIDE by punching THROUGH a closed section of the soffit. That section of soffit is 4 feet from any vents. FWIW, it is not the optimal solution but it is extremely common where I live because of heavy snow and ice buildup on roofs which can block roof vents; it does meet code, and it is a hell of a lot better than no fan at all or just venting into the attic as so many nimrods do. Our upstairs bath fan is vented out through the soffit because there was nowhere to go in a side wall due to the angle of the roof, going through the roof would have tripled the cost of the installation, and going through the gable end would have made much too long a duct run for the fan we needed to use. (Long story I will not go into here.) Since our house had continuous soffit vents, the vents for several feet in either direction from the outlet were blocked off so the warm, moist air wouldn't rise back into the soffit. There is a special duct outlet made specifically for going through a soffit, it looks like a short (maybe 6" long) cylindrical pipe with a grille at the end. A hole is cut in the soffit, the outlet pushed through from the outside and glued in place. Then the duct is attached to this. One with a screen inside the grille will keep insects from coming in and taking up residence in your attic. Make sure you use insulated duct so you don't get condensation in the duct (and be careful when you open the box with the insulated duct - it's packaged compressed and ours sprang out like those peanut cans with the "snake" inside!).

"energy_rater, if you vent the humid air from a bathroom to the soffit, what's going to keep that moist air from going right into the attic?" back draft damper attached to bath fan housing. venting attached to back draft damper. venting exits soffit to exterior. fan being on will push air out of venting, venting to exterior of attic will keep moisture out of attic. also, if you ever take off the cover of the bath fan from inside the house..there is an oversized cut in the ceiling that is covered by the cover of the bath fan. sealing this cut is recommended to keep attic air/temps/ insulation particles out of houses. I use Hardcast brand mastic tape #1402. I also use this tape to attach back draft damper to housing of bath fan for air tight seal, and to attach venting to back draft damper. best of luck.

Thanks PPF, I saw those. They say its is for 3" and 4" but it has a 4" hole and no sleeve mechanism. So my 3" duct penetrating through the roof will have to be enlarged above the roof cut and somehow joined to the receiver in the vent cap. There is <3/4" clearance between the base and the 4" receiver hole in the unit to accommodate a reducer without having to cut 4" into the roofing deck to make room. Reducers with clearance to join both ends would need 3-4". I can either fashion something and tape it all up and hope for the best or I can simply extend the 3" pipe into the 4" receiver as far as possible and hope that the general seal around 3/4 of the base of the unit is enough to allow the venting air to activate the baffle and exit without too much bleed. The unit also seems to have a really small base which does not provide much flashing surface to mount under the shingles. May not be a concern but it does seem to be narrower than other models. Thanks for the suggestion. I will have to think on it some more.