Also. I can order the Tier-One QD mounts - but they are
Because we've not had any of these in Canada, it's hard for me to comment as I've not used it as a clip-on. Your best option is to join the DNT Optics USA User group on Facebook, and ask your questions there as they have employees at DNT on that page that actually use the product daily, and can answer all your questions pretty easily. Search on Facebook for this group:
DNT Optics USA Info/User Group
You can also join this one and ask:
DNT Zulus and ThermNight Night Vision User Group
Sorry I don't have more definitive info.