I've only been using the ThermTec Huntpro 650 a couple of weeks, so still early days but......regarding alignment, this is quite easily checked by aligning the glass scopes cross-hair with icons within the thermal screen. Initially, I was simply using a dot on the objective bell and a dot on the SmartClip - and that works well enough but this can be double-checked with icons on the thermal screen.Spot on. I believe repeatability was an issue with early mounts but current "modular" offerings such as the Rusan adapters and mounts are significantly better. I leave the female portion of the adapter permanently mounted onto the scopes (I have 3 - one fitted to each CF rifle I use the clip-on with) - this does mean that my nice (expensive) Swaro obj covers are removed but as I carry muzzle down, this isn't an issue. The male portion of the Rusan adapter is mechanically tightened against the clip-on's thread (only one adapter needed) and is bombproof, hence when marrying up the 2 and rotating the locking lever, it cams the thermal always into the same position. Having set up the Reference Line in each of the 3 profiles to allow for issues between the different scope adapter sections, each profile matches that particular adapter and mount. I did check the Reference Line after every mounting when I first got the clip-on, but no longer do this every time as its simply not necessary. Hope that helps?
I do like the idea of Peter's Rusan adapter though - takes out any guesswork.