Myself and the unit Maintenance Officer were en route from Pisa to Venice in support of a multi-service exercise. We were at 12,500 MSL, over the Alps, in IFR with zero, zero. The Blackhawk requires 2 pilots to effectively cover all problems. Since we were maintenance we didn’t have a medic on board however our crew chief was a very attractive SP4 and we were all good friends. Well into the mountain range she asked if one of us would jump in the back and assist her in qualifying for the MHC. I asked if my copilot if he would mind and I thought his reply was not sarcastic enough to convey his concern with flying solo. I unplugged my mike, unbuckled and climbed into the back. We left an open mike so my copilot could enjoy the dialog. As he listened (and occasionally sneaked a peek). He then decided to get even by rocking the cyclic in every direction. Ultimately I returned to my seat at which time the crew chief popped back on the radio asking if he’d like a turn. For all the afore mentioned reasons, and not looking forward to being number 2 on the pass, he declined. The 3 of us have continued to remain friends, even after a less than formal debriefing.