Widening the ports doesn't change timing, raising and lowering does, as does lowering the jug.
It's not such a great idea to just go wailing on the cylinder, it's best to have a plan as to what you want to do in terms of how much, and even know why! Restraint and control are a key to success in modifying a work saw, as well as careful workmanship. The best mods generally are ones where the ports are evenly done on both sides, well balanced, and the top is softly rounded so that when the ring passes over, as in the case of the exhaust and upper transfers, it leaves and returns to the piston groove (ring bulges out when passing over port opening) smoothly and gradually. The chamfer on the port edges prevents the sharp ring edge from catching on the port edge. That will damage the ring quickly. A good rule of thumb for a work saw is to widen the exhaust to 68-70% of the cylinder bore, IF YOU HAVE ENOUGH WIDTH ON THE PISTON SKIRT, and ENOUGH MEAT ON THE OUTSIDES OF THE PORT. If the jug has been lowered, raise the intake by the same amount you have lowered the jug, or raise it until it is just at the bottom of the piston skirt when the stroke is at top dead center, might as well capitalize and get as much gas as possible flowing into the cylinder at the intake stage of the stroke. Widen the intake as material allows, considering the rule of thumb as mentioned. Probably best not to lower the intake at all, you've already done that by lowering the jug.
Raise the exhaust by as much as you've lowered the jug, or slightly more. Too much and you'll have a higher rpm saw, but it won't cut the mustard as far as torque, might fall flat on it's face when under load.
Engine engineers are smart people that know how to get good performance out of stock engines, so remaining within or close to what they had in mind with the stock timing, will give a good working saw, that won't have it's life shortened, generally. If you do all these things well, then you likely want to get on to working on the piston at some point.
Regarding measuring squish, use a soft electrical solder, not the hard kind of solder. Sticking through the exhaust is OK, but the piston rocks on the connecting rod, so just measuring one side can give a false reading, you want to measure on opposing sides, or on four opposing sides is good, as the cylinder bore may not be symmetrical to the base.
I believe you'll get advantage by running high octane in modified saws, and a richer oil gas mix, say 32/1, is likely a good idea too. That's a bit controversial, as well as using dino or synthetic two stroke oil. Opinions may vary.
There is some supplemental reading I can recommend on two cycle engine performance modification, if anyone is interested.
It's helpful to know how to measure timing on the engine, usually done with a timing wheel.
You can take a sharp pencil and outline on the piston the inside shape of the stock port openings. That will tell you how much you can remove off the port. The general rule of thumb is to leave a minimum of 3/32" of skirt width covering the port.
Have fun...modded saws rock!
Jay