I made a pair a while back - cut down the sticks, screwed in some velcro loops - thwaka, thwaka.
I wasn't digging the wood on the strings sound, so I used a little rubber tool-handle dip on the tips. It "cooled off" the attack a bit, but looked pretty ridiculous - like I had giant red fingernails.
None of my stuff sounded as cool (and developed) as Mark's stuff, though.