I'd be using mastic, whether you intend removing it later or not. Asbestos is essentially only dangerous when it can get into the air. If it is bonded safely, either by painting a flat sheet, or using a bonding agent such as mastic, then the danger is effectively zero.
However, I would also investigate getting it removed. Longer term it will be a cost, either to you or someone else, who will factor in that cost when buying your house.