I may be late to this party but, for what it’s worth, I’d go with the sling mount. My 30cf pony was originally a tank mount, and I never really liked it, always felt like that little extra weight was uncomfortable. I know many of my buddies use it this way and are ok with it but I wasn’t. So, I was planning a wreck dive in NJ last year and decided to pick up a sling mount and give it a try. It wasn’t expensive so why not see for myself. Man....am I ever happy I did because it simply disappears during the dive. Really, I don’t even know it’s there. I thought there may be some balance issues because of it only being on one side, but there were none. Also, I like just peeking down and seeing the reg and spg right there. Very comforting you know.
I can only suggest that you experiment, especially when it’s not hard or expensive to do.
Neil