Can't comment on urac, I have never used it. But I bet Brandon from Rose Oak Bows knows what he is talking about, from looking at those beautiful bows.
But if you want to use smooth-on, KTinAK has a good idea. The smooth-on is good glue.
From what I understand, the smooth-on will cure at room temp. I was under the impression that it has stronger bond with heat, but I can be wrong.
Once smooth-on (epoxy) is cured, it's cured. Putting in a hot box will not do anything positive for it.
For the riser, it's short. It will fit, so use your oven, put on low temp like 170 or so. If in doubt, use a meat thermometer.
Then, you won't have any doubts.
Dan
ps-line the bottom of your oven with tin foil