Greetings ! The HUP applies within QM. But, the HUP is not part of GR. Gravity is not part of QM on the other hand. In QM the only method of interaction we deal with is the electromagnetic and extended theories deal with the nuclear forces. But, what about using Gravity to "violate" the HUP ? I know the necessary microscopic scales and the weaknesss of Gravity as a force probably prevent us from making any relevant experiments, for now. But, how has this specific issue been adressed so far ? And what potential experimantal ideas exist ? Live long and prosper.