Most of the Huskies take to modifications somewhat better than most of the Stihls, or so the story goes. It's probably because, more than anything, the amount of transfer volume the current Huskies have with four tracts. The newer Stihls now have "quad ports" as well. Another factor is how tight the saw's wound from the factory. More can always be got out of a motor, but some of the factory saws leave less to easily get. Your biggest gains will be gotten by letting the thing exhale with less restriction.
I still say that if the engineers felt more power could be had with less weight for an amount of reliability they're willing to stand behind, we'd see it from the factory. In other words, I'm kind of in agreement, in principle, with your mechanic. That being said and having run some of Dan Henry's saws, well, they do put a big old crap-eating grin on your face.
You must have someone a lot closer to home than the States who can do the work for you. It's not exactly rocket science or anything, though it is something that generally has to have a bit of time investment as well as friendly predecessors to help with some particulars. Most everyone here who does such work are good and generous folk that way.
Glen