Tippett and RonW...
As to overlays, I looked at a "surround piece", i.e. a wood piece that doesn't cover the hinge, as Tippett's does, but builds up to it's surface, but decided it wouldn't really be practical on the narrow back surface I leave on my risers. I had barely 1/8" to either side. Also, I have a small hand and didn't want to end up with too deep a riser for comfort. Instructions are not to actually inlet it, as this would compromise the riser strength. My flatbows already have pretty minimal risers.
To me, it's pretty strictly an appearance issue. I find the grip, with the hinge, quite comfortable. On the Black Widow I had that had this hinge factory installed, there was a simple rubber roll up grip cover that worked well and covered/hid the hinge. These are available, so I'll order a couple and see whether I end up preferring with or without.
As to difficulty, if you'd asked me last week, I'd have said "Yikes!" However, if you read my pages, you know I approached it pretty systematically, doing a test installation on an old riser from a broken bow, then a build from start, and finally doing the conversion of an existing bow. (And, yes, that was a very nerve wracking decision!) With that practice experience, and having spent a lot of time thinking the job through, step by step, over and over again, I would say that the actual difficulty was no more than a 5 or 6. I would look at doing another as just a fun way to spend an afternoon.
Read and re-read all of my info. I did my damndest to show every consideration I could, including every mistake or mis-step I made. I'd really like to think that's of benefit to someone. Approach and carry out the work slowly and carefully. Figure out the positioning of the hinge in relation to the lamination joins and study the depth of the riser in relation to the screw length, and I think you should be able to do most longbows. The biggest potential problem I would be concerned about would be if there is much curve to the back of the riser. If there is, you might have to flatten it some, and again, you'd want to consider whether you were compromising strength.
Good luck, and let me know if you do it.