Getting the flywheel off is not always easy, experience makes it somewhat easier. In your case it is not really necessary in that there is no other location for the module to be mounted so it is located under the flywheel and that makes the saw a 120 Super. I find the 120si has better porting that makes it feel snappier acceleration over the 120Super, my 120Super seems to have more grunt or torque and can be lugged down and just keeps pulling. I would chose my 120 Super for a milling saw if needed. I mill with a 90cc Solo and a 066 Stihl, some day I may mount my 090 to the mill frame. Sach Dolmars were always very well built chainsaws, I had a 7 year run with them cutting commercially, they performed very well for me.