Received the tube rings for my SM90 today. I ordered them from Peter Tan who has them manufactured in standard and custom sizes. The SM90 OTA is 110mm dia. and I couldn't find any to suit in this size. They weren't cheap at $140 delivered from HK but they are beautifully made in black anodised aluminium and fit perfectly. Around 2 - 3 weeks delivery. The rings will be much more versatile and lighter than the existing clamshell although I will have to find a way to fit the solranger finder to the rings.
