All contracts are considered to be individual, so I would think you could. Then only snag might be if it would result in less than 150, but I don't think that would matter either, since they allow resales to new members with less than 150 points.
hi Sandy... the answer is yes, you can definitely sell your master contract and keep only the add-on(s)... even if your leftover add-on(s) amount to less than 150 points. no snag at all.
As noted, the answer is yes. However, carefully consisder how many points you need. If the add on is less than 50, consider selling it first or at the same time. Good luck.