First, curl force and breakout are different.
Second.....yes all bets are off on possibly destroying something, or overloading front axle if you increase cylinder diameter.
The holes you picture I wouldn't use. They might just tear right out too, with no pin-boss for support.
The MX uses bar linkages for dumping. This is to increase the range of travel. And yes, curl is a bit weaker as a result.
My l3400 had cylinders directly coupled to bucket....alot stronger curl in relation.
Your cylinders that are 10" longer.....it's possible you could do away with the bar linkage and couple direct to bucket (ssqa adapter).
And also.....if the cylinders you already have and want to use are 1/2" bigger bore.....that's great.....but what's the rod diameters? Because you are retracting to curl