It amazes me how poorly car seats and vehicles are designed to work together. I have a 2 and 5 year old and the rear facing seats are a pain. Don't use the side seat latch loops for the middle seat as there is too much side movement. With two infants, there shouldn't be a seat war issue (for a while anyway) until they are forward facing and then there is not as bad of a problem with having a kid behind you. It's like having a custom seat massager.

If you didn't get the type that you leave the seat base in the vehicle, I would also recomend taking them back and getting the base style. Buy your 2 complete seats and get spare bases for the wifey's car and a spare set to loan so you don't have to swap them all the time (When, of course, you finally get to go somewhere with the wife without the kids:-laf). I could put a rear facing behind me (Graco) and only loose a few inches of leg room and I am also 6' but a little bigger boned than you. Also, I like the blue with yellow handle seat belt ratchet that Babies R Us carries for the middle and non-latch spots. I don't like much seat movement and Grandparents and others never seam to have Latch loops, or they are in the wrong place. Also, there is no such thing as too tight. Stand on it, jump on it, whatever it takes, but it should have minimal movement. No offence ladies, but I have never seem a seat put in by my wife or Mother-in-law that was tight enough, and they can hardly ever get seats I put in out. I guess pushing a release button is asking too much.

Also, don't cheap out if you are going to drive them around much. I bought better seats, i. e. better padding, when we moved from Dallas to Atlanta and was amazed how much less of a struggle it was getting them into the seats. They were finally comfortable. Congrats on the two little ones and enjoy them. It's going to go twice as fast for you.
On Edit: My '03 only has Latch loops on the outside seats. To use the safest spot in the truck (middle) I had to use the seatbelt and the ratchet from BRU.