BHO in a 510 cartridge...

edit: figured it out all by myself... lol

Not sure, but last time I was going to attempt it, I got some PEG400. Its made to suspend thicker oils, etc. 1 to 1 ratio of the base to BHO. That, and I think you could mix directly with some kind of terps they sell.

You could get good bulk deals on empty carts back then. This was years ago, and I still haven't turned to the dab side.. Good luck.