Honestly did think about the excessive weight hanging off the front of the scope. Will look at a dedicated optic as well and see what I can find.
Plenty of dedicated thermal scopes that do reasonably well, even with 320 sensors. Unless you would be happy never using a 320 one at no more than 75-100 yards, you need to look at ones with a base mag of at least 3x, with that even a 320 sensor one would be fine out to 175+ yards and useable somewhat beyond depending on manufacturer and how good their image processing is and how good a display they have. Dedicated thermal scopes are so much better than budget clip ons it's like they are two entirely different technologies. If you want warranty support in the U.S., berring optics might be the place to look, they are in Texas and service their products there, something to think about over manufacture's like Iray, agm, etc.. A really nice one they offer(relatively speaking on the budget side) is the super hogster A3 384 12UM 2.9-11.6X35MM, just looking on the web they can be had for roughly 3.1k, and most reputable night vision dealers will beat their own advertised price if you call them on the phone, some brands they don't have room to do that and I don't know if berring optics is one of them. I think the best image quality in the lower budget range comes from Iray, chinese unfortunately, but they do have their image software and displays a step above most anyone else. If you can deal with chinese made thermal(not my cup of tea), worth a look, supposedly irayusa located here does do warranty work if needed, I don't really know.
I'd stay away from any that have dedicated internal batteries(what do you do when the battery loses life or fails, you are SOL) or any that only use 123 batteries, they are expensive/don't last long/and if they do take rechargeable 123's, they have very low capacity. I'd also stay away from ones that use proprietary battery packs, the markup on those things is unreal.
Little known fact about thermal, look it up and don't trust me. They all degrade over time, the better built and sealed they are the longer they last, and that can be way over a couple decades for the best of them before degradation could even be noticeable. If I was shopping on a budget for one, I'd keep it in the refrigerator when not in use, seriously.... Look that up too, temps in the mid 30's are best temp for storage on thermals. That is one of many of the reasons military thermal's are so expensive, they are built like a tank and sealed so well this is not an issue with them.