Code requires an 1-1/2 trap on a tub. You may increase to 2" but you may not reduce below 1-1/2".

gildomilo, are you using copper pipe? If not, are you aware that its outside diameter is smaller than the other kinds of pipe. Also, are you aware of Street elbows? They take less space than regular elbows. There is more to share. Post again, describing why 7" is not enough. I hope you can fit a 1.5" trap in there.

I fit the 1 1/2 in, the drainage and overflow had to be cocked a little to the side in order to fit. The problem is where the shower vent line had to go and the framing in the bathroom. It's in, now I just need to seal up the waste and overflow.

I am curious as to how you connected the shower vent?

Just down stream from the trap, maybe 2" is a sanitary tee the vent comes off of that and goes up, the rest of the drain continues along the path to the stack. The tub is only 30" wide, and the framing is very tight. In looking at the framing I probably could have pulled on of the 2X's out and gotten enough room for the drain to go straight. I might do that today, but I hate to as I have the tub and everything else set.

I decided to fix it the proper way and take the old framing member out. So much for the bath I took yesterday :)