Im not very familiar with the 2009+ F150, but Im pretty sure the backseat folds down. As for 6.5" vs 5.25" speakers, try to get the 6.5" to fit if you can. Again, I haven't done an install on the newer F150s yet, but Im pretty sure you can make the 6.5 fit with an adapter plate which those Alpines often come with. Make sure to get an amp on them, they like power.

Hey, i noticed you have a pretty good knowledge on speaker setups in our trucks. I am in the process of building my system and had a few questions you may be able to answer. I am looking at putting in two sets of the Alpine SPR series speakers, specifically either the SPR-17S or the SPR-13S. My question to you is what size should I go with? The 6.5 or the 5.25 speaker and if I went with the 6.5 would I have to modify anything? It may help to tell you I have a 2009 Screw FX4. And also, does the back seat on these trucks fold down? I cant seem to find an answer anywhere on how to do it. Thanks!