Backpacker magazine lists 10 considerations before you buy. Among them:

Measure your tent. In many tight two-person tents, full-length sleeping pads overlap at the feet, which means you’re carrying some mattress that you don’t need. One solution is a mummy-shaped pad; another is Cascade Designs’ Link Rest system (see The Minimalist Bed), which has interlocking dovetail edges for linking several pads.

Initially I thought you could just go with the stated measurements of your tent but it seems you’d be far better off getting it set up and doing a real-world accounting of how much space you’ve got.