A couple of years back, several whizzes worked out the combat formula for Civ2. So with a lot of help from SlowThinker, I made an Excel program to calculate odds. Think it can still be found here:
Boco's Apolyton Upload.
At the time, the testers decided that the bonus was 1.5, and only worked for 1hp, 2mf units. IIRC, someone (M de Sodaq?) indicated that the bonus applied if the fp>2. DoM's results, however, suggest that the piker bonus does indeed require fp=1.
In DoM's tests, the calculator comes up with the following:
Test 1: 4a,1h,1f vs 4.5d,1h,1f -> 43% chance of successful attack
Test 2: 4a,2h,1f vs 3d,2h,1f -> 66% (i.e. no piker bonus)
Test 3: 4a,1h,1f vs 3d,1h,1f -> 61% (i.e. no piker bonus)
Test 4: 4a,1h,2f vs 3d,1h,2f -> 61% (i.e. no piker bonus)
It's pretty important to have a large sampling to get representative results. Those same testers often used >100 tests per condition.