I have no want or need to port mine or to reduce "squish" distance. It's already a huge PITA to start (no compression release) as it has over 170psi cranking pressure. Had the muffler off once, P/C is mint condition. I haven't used the saw much in the past few years, bought an Echo CS-600P and CS-590 and beating them to death instead. The Echo's are better suited to the type of work I do here, cutting up tops left over from logging operations, although I've got scores of HUGE dead Ash trees to deal with this year. I was going to leave the Ash trees as they are pretty much standing firewood, but big limbs are starting to fall out of them and I don't want to be walking with my 3 year old grand daughter and the dogs and have one come down on us. Just the other day we were building a bridge across a creek to access the other side for firewood and the next morning when we returned to finish the job there was a HUGE Ash limb laying right across the bridge we'd been working on. That did it for me, took down a dozen Ash yesterday and going after the rest of them this weekend.
Anyhow, I'd add here that my 268XP is better suited for big work, as it is happiest with a 20" bar completely buried in hardwood. It has a someplace "narrow" power curve, absolutely LOVES to run at really high RPM's and you have to keep it up there as the power (torque) curve is concentrated in the upper mid-range and top end. It doesn't "grunt" all that well and not happy when the RPM's fall out of where it makes it's best power. Not trying to make a negative comment about it, but it's a "race horse" and loves to run, not really happy doing anything else........Cliff