On the 260 don't go up or down more than about .040", most of the gain will be widening the ports. Raising and lowering too much will change the horsepower band, widening will increase the torque band.
Take the cylinder off, remove the base gasket then hold some solder on the outside edges of the piston with grease, four places is best, three will work, put the cylinder back on and rotate the crank twice. Pull the solder out and measure the thickness of it. Anything less than .019" on that engine needs a gasket, but I doubt it will be that tight. Most of the saws I've done, Husky's, come right at .019-.022" without the gasket, Then I use an Anaerobic sealant,
https://www.fcpeuro.com/products/anaerobic-gasket-maker-51813?gclid=CMGk4PihiMUCFYyTfgodTxEAyg instead of a gasket.
Now on widening the ports, in the .066 vid he talks about the skirt width, but you will also have to keep in mind catching rings, not only do you need to round and smooth all edges inside the cylinder, you need to keep it under 80% of the piston width. Any wider and you have a chance of hanging up the rings and breaking them!
The muffler, try to stay around 75% of the exh port diameter, keep a little back pressure on it.
Shouldn't be any need to re-jet the carb at this level, cut off the limiters and adjust it until it's happy. A little on the rich side isn't a bad plan.
The 192, meh! I can talk you through a muffler mod, but I can't say I'd waste much more time than that on them silly things! Terribly hard to work on, terribly finicky about any changes, just a real pain in the ass all the way around! Once you start looking at it, I think you'll agree, it's just not worth the hassle.
Keep in mind, this isn't the rocket science, or black magic many want you to think it is. I had a Husky 346xp that I'd been into three times and still wasn't happy with. One night I was drunk, had some good music on, the weather was nice, so I tore down my Husky 350 and ported it. I still have the 350, but the 346 is long gone!
