XJ550 rear suspension travel question

Hi Guys, - first off thanks for all the great info on here, I've been reading steadily since I picked up an 82 xj550 that I'm making into a cafe-style bike (first motorcycle build).

In modifying the seat frame (cut the back of it and crossmembers off, welded new curved bar on back) I realized that I should add another under-seat crossmember (in the area where the paint has been ground off the frame in the pic) for additional structural integrity, but noted that there is only about 4" of clearance between the back tire and bottom of the frame. Does anyone know how much suspension travel the rear swingarm has with stock shocks? I searched here and on the internet but wasn't able to find any info.

I'm thinking I will have to make an arched crossmember, but if I can keep the seatpan template flat that would be preferred. Any advice/input would be appreciated.

Thanks!

 

http://www.motorcyclespecs.co.za/model/yamaha/yamaha_xj550 81.htm

 

that would get you left/right strength. think you really need it? maybe a flat bar farther back, just to hold the seat up is all you need

 

Thanks k-moe. I can't believe I didn't see that when I checked the motorcyclespecs website.

Polock- I was thinking that a crossmember would be good since there was a raised one I cut off. I think it will be good for left/right and torsional forces, as well as providing a place to secure the seat pan.