Is your jug oem?
I’d like to know how you are exactly measuring your squish and timing numbers.
For port timing, the only accurate way is with a pick and ring position (as pushed in jug by piston crown) after a zero’d in degree wheel. The second most accurate is using a micrometer and timing software. Least accurate is visually looking into ex port for roof and transfer closing. Looking through plug hole for light to come through ex roof is slightly better, but still inaccurate.
As for squish, you need to use a solder that’s soft and closest in thickness to calculated squish. If you are using .060 plumbing solder, there will be springback and an artificially large squish. You also have to rotate the piston enough times. If you are on the money, you should stop feeling any contact with the solder at all with rotation.
I personally use .6mm solder (.024) and a drill to turn motor over from the PTO side of the crank.
Not an expert by any means, but I’ve been inside over 50 of the 1121 models. Squish in the 44mm jugs (all 026 and early MS260) is generally .006ish without gasket. On the lare MS260 44.7mm jugs, it’s more like .017 without gasket.
I‘ve never seen an ex roof lower than 98ish on any 1121 jug. Even with taking .065 out of the chamber flat and cutting base for a true squish of .015, I’ve struggled to get the factory oem ex roof below 103-105.
I’d recheck your numbers. YMMV