I've bitten the bullet, and AH3 I start firing before convergence which uses up ammo but lands hits.
Make an appointment with morfiend or kingpin in the TA so that you can turn on the lead computing gunsight and they will let you throw rounds at them all night while giving you feedback.
My experience with AH2 vs AH3 is the timing is a tiny bit different. I've set the mil file number for my 100Mil ring to 272 from 256. Seems you need just a tad more lead on deflection shots. 5, 10, 20, 30 degrees off in AH2 are more like 8, 15, 27, 35 in AH3. I know nothing changed in the code per Hitech, so it must be me getting whiter in the beard.....