I got them in my last house for the room over the garage and have them in the house I am building now over the master bedroom (the attic space will be my craft room) and over the garage (storage). The master bedroom is 20' wide and I ended up with a 12' wide room. The ceilings are a little lower than I had hoped; they are around 7', but for a craft room, it's fine. My trusses are spaced 24" OC and I wish I had closed that spacing up to 16" OC to give the attic floor a little more strength. I am probably going to install 3/4" oak floors up there to give it a more solid feel. I am very happy with the extra space I got for the little extra I paid for those trusses. There is a pull-down stairway to access the attic over the garage, but I will build a 6" wide stair case to the craft room after the final inspection. Because of the layout of my room, the stairs wont meet code. The rise and run will be a little off. Still safe, but not within code. If you want stairs to get up to that attic space, make sure your truss engineer calculates what it will take to cut the bottom cord of the truss to permit a stairway.

I just purchased 30' wide, gambrel attic storage trusses. Paid $104 per truss. They give me a 16' wide by 8' high attic. Spaced 16" on center I get 100+ psf floor load. I know its not exactly what you are looking for, but it might help.

make sure you nail or screw them down. my stepdad put flooring in his attic and did not nail any down. it was only where stuff was to be sitting, not for walking on. well, after moving stuff around and throwing out a bunch, the floor is now walking area. last time i was up there one of the boards went out from under my foot and i ALMOST went thru the ceiling. the boards are now nailed down. in many areas we doubled up 1/4" and it is fine. any more than a 16" spread needs to be 3/4".

Keep storage over garage. To install flooring over the living space you would compress the insulation and you need what you have in texas! I like to screw the plywood decking down in case you ever need access to anything below. Size of framing is important, because of weight/span. I don't think anyone starts putting stuff in the attic with the idea of storing a lot of stuff..but a lot of stuff sure finds its way there over the years. Always be careful working in the attic, Make sure there is enough light to see where you rest you tools and put your feet. oh,,,and cut plywood in half two 8x2' pieces so that it goes easily into the attic. I have to cut into 4x2 because it is heavy,,but your big guy wouldn't have that issuel best of luck.