I'm looking for the same answer. A local, independent home improvement store warned that heavy, mirrored bypass doors with a floor track would buckle the floor if it's not free to float when the door is attached to both the hardware and laminate, subfloor, or substrate and the floor expands without allowance. My closet opening is unusually wide at 96" so the doors would be heavy. I am loathe to drill an oversized hole into the Pergo "Outlast" for either bypass doors or replacing the original, lightweight bi-fold doors and and use a washer for the center bi-folder door point. Bi-fold doors are lighter and the advice I've found is to glue door guides towards the middle of a track if hanging doors, or affix a track on the floor held with double sided tape if not a hanging door. See this video for the former, hanging style-door-w/glued-guides approach: https://www.youtube.com/watch?v=C-3ZvXhfE3E&feature=youtu.be Hope this is helpful.

These are from HD, since they have 15% off custom doors right now. Top track supports the weight, bottom track is a guide. They suggested (and I read on a couple other forums to...) carpet first and install the bottom track over the carpet. That seems strange, and means I can't order until I know how thick our carpet will be. Also the track will be smushed down on top of the carpet pile? That doesn't seem nearly as solid as putting down a permanent filler strip of plywood, screwing the track down to that and carpeting up to the strip then starting again on the closet side with a fresh edge of carpet. I always thought doors first then carpet... but in the case of slider rails it's the opposite?

PGT owns CGI but we are PGT distributors and I have never seen CGI products so I can't comment on what product line is superior. #1 I am a big fan of the PGT vinyl sliding glass door and a 3 panel three track would be nice for that opening. As far as the aluminum the 780 door is nicer than the 770 #2 yes if you add tint the solar heat gain goes up. In the case of the PVC door with the Energy Shield Max your solar heat gain goes from .19 to .24 when bronze tint is added. #3 Argon gas retention is very good with the spacers used today. #4 I have never heard of a higher risk of breakage with argon. PGT uses stainless steel screws but you need to upgrade to stainless rollers on the PVC door and the Aluminum 770, the 780 is standard with stainless rollers. #6 your factory order and NFRC sticker on the window will list the type of low-e and the performance numbers. I suppose you have to have faith on this one. Below is a link to a PGT vinyl 3 panel 3 track door in operation. https://dl.dropboxusercontent.com/u/39410396/PVC%20Multipanel%20Sliding%20Door%20Video.MOV

NafNaf--Forgive me I am not sure what is different in what you are suggesting? Virgil-- I am not good with the descriptions, but the the house sits in a hill and the sunporch is above the basement patio at least for part of it, the garage is under the house. The lot is pie shaped with the great room facing the narrow end of the pie. I have been working on this all morning and moving furniture in my current living room and measuring and graphing again to double check. Right now my plan will fit a 7.5 x 9.5 sectional facing the west wall, that wall will have built ins and house the tv. The far end of sectional will be about 8' from the TV, this is the exact set up we have in our current home and the configuration is very cozy but nice, also the "L" will be open to stairs, hall etc so not closed off. On the fire place end, I feel like I can set furniture(possibly a pair of 4' settees arranged opposite or a combination of smaller chairs and a settee) about 4' from the back of the sectional and comfortably flow between the sitting areas on the stair side---I measured with the swing of the doors etc. I am keeping in mind that yes its tight if the doors are open but that will not be often. So with my furniture arranging I realized that the slider will just not fit, its much better with large windows that open. I am thinking 4, 6' casements.