Hi mcphillips, The Scarlett has a choice of either line or instrument for each of the two channels. The jacks are the kind with the XLR and 1/4 in the same part. The phantom power only goes to the XLR pins so you don't have to worry about getting juice on the phone plug.

scarlett2i23quarter_1.jpg

Impedance aside, I'd never heard of a dual-mono before. I'll bet American money that when I get the ohm-meter on it, the sleeve is shorting to the ring. The 3.5mm looks like every other stereo plug in the world. If it isn't actually that, the 1/4" stereo adapter is going to get confused.

The other concern is that if the impedance is still badly mismatched, will a stock 3.5 mm male to XLR-male adapter be putting DC on the lav? With the 48v on for the other mic, the pins will be charged. sh