where is the best place on a 29 for these? (a pic if your ve got one), im looking at getting a set that come as just the bung and have seen that all is needed is an m10 1.25" thru bolt, is this a good idea. they are 50mm.

1 bolt is longer than the other. when i needed to replace the longest bolt. i went to a nuts n blots place and they said it was a custom made bolt and they could not get them in.
its better to buy the whole kit...
you also want to consider drilling a larger hole so the panel slips over the widest part of the bung for easy maintenance access.

It is difficult to get the bolts! Your average fastener joint doesn't stock them: "Nah mate, they're fancy Japanese bolts". I ended up re-tapping mine to take a standard bolt - did the job.

just get the WHOLE kit and be done with it...