If I may add my $.02...
I bought some of the leather belting that Duane at Wyatt's Musical Americana sells. At first I thought I wouldn't like it because it was slightly curved (along the parallel long edges). I followed his instructions
http://www.wyattsmusical.com/belts.html; stretching it, finding the length, scarfing the ends and gluing it, etc. BUT, Instead of using a scarf joint I used a lap joint because, for me, it was easier to get right with a straight razor lying flat on the belt to remove the leather for the joint, working AWAY from your fingers. Also, I used Aleene's Tacky Glue, instead of contact cement because I have a lot of it on hand for re-coning woofers.
http://www.michaels.com/Aleene's%C2%AE- ... lt,pd.html
I'm VERY happy with the results.
Like Phonofreak, I pinched the joint together with flat needlenose pliers to not only ensure a positive contact for the glue but to also promote a consistent thickness at the joint.
NOTE: The image below is leftover belting that I thought was too curved. The photo of the belt on my Amberola D X was the very first belt I made. It looks like it is coming apart, but I assure you, it isn't. I just wound up with a slight gap in the joint. I subsequently learned to cut the joint about β
" long so I could fine tune it lengthwise to make it shorter if I needed and, no more gap.
I've done 4 belts in the past month this way. My Standard A, Home A, Amberola D X, and Graphophone Q. No slippage on any of them and, incidentally, the shiny side that ends up "out" has a cracked appearance that looks aged. I think that's neat.
My point is this is so very easy, and being as simple as this is, I
personally see no reason to use a rubber O ring, and it looks right.
Of course, YMMV,
Fran