We use a Crown PZM (what you referred to as a "boundary" mic) to amplify the congas, bongos and dumbek through my PA system. What we've found works great is to mount the PZM onto a 24"x24" piece of 3/4" plywood, with a piece of thick carpet on the back-side (de-couples the board/mic from the floor, thereby reducing "walking" noises), and then place it on the floor directly beneath the conga and bongo/dumbek stands.

We've also used a pair of PZMs for recording, usually by placing them on opposite walls (for adding "room" sounds to the mix, while close-mic'ing vocals and acoustic instruments...bass we run DI.)

Handy little devices!