Finger drumming, as popularized by performers like Jerry Ellis is very doable on your iPad. However, as you see here in this video from Mohd Ekhwan, it can crack your screen! This is visible in the first few seconds when the screen is off.
As you also see in the video, playing on a mattress provides a nice little bounce in addition to cushioning your percussive force! That bounce is really nice, and one of the few advantages MIDI Fighter has over Maschine and MPC-style controllers. The arcade buttons on the MIDI Fighter bounce right back up to your fingers, allowing you to quickly hammer back down on them. It also makes for a nice bit of natural rhythm in the performance. I like Mohd's solution here of bouncing the whole device!