Howdy. Let me preface this by saying I'm a fairly newbie Kerbal player; there may be a difference between how I think something should work and how it does work.
I launched a very small probe consisting of the Probodobodyne OKTO with the Double-C Seismic Accelerator, 2HOT thermometer, and PresMat barometer on one side (0.02t) and the DMagic Magnetometer Boom on the other side (0.02t). Once I get into space (>70,000m), I try to vector into orbit with a RE-A12 Pomeranian (a 0.625m LFO gimbaled engine from some mod; I don't know which).
The problem is that the craft immediately starts to spin pretty heavily. There's no trim (Alt-X to verify). Once I remove the DMagic Magnetometer Boom and relaunch into space, I power up the engines and continue on without spin. I've repeated both variants with repeatable results.
That's what doesn't make sense to me; there's no air resistance to cause that spin, CoT through CoM *and* the arguably unbalanced version flies straight. Is there something special with the boom that would cause this behavior? Thanks.