We've had 400 watts and 4 T-105s for several years now. I installed the system myself (it's here in Additions) as I couldn't find anyone willing to even get close to following Jack Meyer's advice (
http://www.jackdanmayer.com/rv_electrical_and_solar.htm). We got our four 100w mono panels here:
https://www.renogy.com/ and they make all kinds of sizes. I'd strongly suggest you find something you're interested in and get the actual dimensions. Then go up on your roof and figure out where you can put them. Since you really need to have the shortest DC cable run you can, this should be near the front of your rig (unless you're mounting your charge controller and batteries somewhere other than the front part). There's a lot of stuff on our roof that mandated using 100w panels so I could locate them best. I had to remove our MaxAire vent covers to avoid shading. You also don't want them completely level - a little slope lets rain water drain better.
Although I made certain I could add up to four more panels and two more batteries, it's worked very well for us as is. I put a thread up in Boondocking about spending four days with cloudy/rainy weather a while ago. Unless you just have to use electrical appliances (coffee pot is the worst!), or are in really cold weather so the furnace runs all night, a little care managing what you do will make it work fine.