How big to make framerails?

I was thinking of getting myself some steel for my birthday(happy birthday to me). I was wondering for making new framerails for my stfbd how big do you guys think I should go. I have been tossing around different ideas. But I think 4 x 4 with 1/4" wall is what I was leaning towards. I plan on using this truck so its got to be strong, I am also tossing around the idea of stretching the cab so please keep that in mind. So what do some of you guys recommend?

i used 2x4 1/4 wall to do my stock floor... plenty fuckin beefy for under the cab. and notches

im with that guy.
The width really has no affect on the strength of the tube on our applications. All the weight is trying to bend the sides instead of the top and bottom. Ive heard of people using 2x3 or 2x4 but i coulsnt tell you about using the 2x4 since ive yet to bodydrop a fullsize. Id def go 1/4'' wall tho with a fullsize truck.

2x4 1/4" wall

just make it big enough to throw alot of sparks

If you have not seen this yet...maybe this will help ya!!

I"m doing a stock floor on a F150 now with a chevy 1500 front suspension, 2x4x.25 is fine. I've seen a few people do 4x4, but thats a bit exesive.

that crew cab ex cab is bad ass on ssm

hell just overkillit . go 2x6 with a 3/8 or 1/2 wall that way you got some to drag off

I made mine out of 3x5x.25 it worked out fine and is stout as hell.