I doubt there's a procedure posted anywhere for it, but it's a mod that lots of guys have done. I will tell you though that it's more trouble than you probably think it is. You have to build up blocks to take the rear bolts, build structure in the front of the wing for the dowels and precisely drill the bulkhead in the front of the wing pocket to accept them (possibly building a bulkhead there if the existing structure isn't suitable), and you have to make the back of the wing solid so the bolts don't crush the wood or pull out. It all has to be done with epoxy and the parts have to be fitted well to be strong enough. Converting from bands to bolts is a pretty big redesign of a very critical structure. It's not impossible by any means, but it's also not a 2 hour job either. Lots of guys start thinking about doing it when they get tired of stretching rubber bands every time they go out, but bolts aren't really that much quicker. The one benefit I see is that you'll get precise wing alignment every time, but you can also do that by making some marks at the front and back of the wing and fuselage to line up. The reason trainers use the rubber bands is because if you cartwheel a landing or nick a tree, the wing will have some give and likely will make it through.