If one is building a period-correct early 60's 5513/5512, no, you don't want the channel. Late 70's maxi dial 5513, sure, it's fine. If you want maximum water resistance, then yes as well.
I'm sure many of these (assuming they will be delivered) will pop back up in sales section over the coming months. Shouldn't there be tagged photos? Just sayin.
Good job. On second thought, I think Hypo cement would be fine. While its out, might as well do the platinum paint mod on the insert. My suggestion is to use flat white manifold/caliper paint. Bake it on, then use silver/aluminum caliper paint. Both from spray cans. Remove factory paint from the numbers with acetone first.
I would use thin 2 sided tape. When removing the bezel, careful about the springs and clicker balls. On the gen SubC, the balls are welded to the springs and are lubricated with a lithium-type grease which tends to hold them in place. The noob balls and springs are separate: You could easily drop them. So make sure you don't tilt the watch from horizontal as you pry off the bezel. Do not perform the surgery over [censored] carpet!
When you are contemplating buying anything over the Internet from a person you've never met or spoken to, only buy something that you could reasonably afford to lose. I've been scammed before. It sucks donkey ballz but you gotta move on.
He has the dials in Singapore I believe but the cases are sent out of Vietnam. Hence the lack of QC. Sounds like a bit of a crapshoot of what you might get.
I have a set of 5513 hands that have a "hint" of green as well: I suspect moisture will turn some tritium lume mixtures green under certain conditions.