My dealer here was telling me they have all kinds of mounting brackets and cargo boxes for the r50x. Its called Twin City Recreation in Lafayette, Indiana. Give em a call. They might be able to help.
As far as the warmup issue.......i'm not exactly sure since i'm not a mechanic but from what I've read.......it could be running too rich or the idle mix isn't correct.....so have someone check your carb. When I start mine, it revs to about 4000 on its own cuz of the choke and then after a minute goes down to 2100 and thats where it stays while warm/hot.