I get that.I also would like it to run 3/8 chain I have a roll stihl chain I make my chains from. I like my 661 with the mtronic my dealer told me to start it with the choke on for 90 sec then blip the trigger then shut it off then restart to recalibrate for the difference in elevation.
90% of the time I run my 661 I like the power of it but for the guys and my wife don’t like the Power or weight of it that sometimes go with me.
We cut just under 100 cords a year for my house and parents. The rest goes to heat my shop in the winter 80x40 farm shop takes quite a lot of wood to heat.
I just buy a bunch, then I can get a feel for them all, it sounds like they need to try them all too, this just might get expensive lol.
Do they like to run the 290.