I'm not sure if you're playing the same game I am.
But if what you described was legal (in a "normal" game of backgammon you can't open with 66) then I think doubling might be ok at that matchscore,
since you can be a bit more aggressive with the cube leading 4-away, 5-away.
It shouldn't happen if you are playing any kind of rules that resemble good ones. But if it does happen, then my thinking is that you should double. Or play NLHE hyper turbos.
It shouldn't happen if you are playing any kind of rules that resemble good ones. But if it does happen, then my thinking is that you should double. Or play PLO Short Stacked hyper turbos.