Okay, making some progress now, almost done with the plumbing...but new question. This one is about durso standpipes, which we are doing for the first time.

Our side overflows have the holes for the drains in the bottom glass. We are hard plumbing some (1" PVC) durso standpipes in there. Is it important for the little cap piece on the top of the straight vertical pipe to fit snugly? We can use the same fence post looking cap that everyone else uses, and it just perches on top but doesn't make a nice tight seal. Or we can use a plug piece at the top that fits snugly.