Chainsaw Repair

Is there anyway to increase the compression on these saws?  I realize it's a clamshell design, just wondering if anyone's had success with this. 


The most I can get out of anyone I have is 155 psi, most are at 140.   I see 026's pulling 180+ at times.  I realize different saw designs and the ability to decrease the combustion chamber area with a thinner base gasket on the 026.

Has anyone ever sucessfully tigged a dome on a piston?  If so, what shape and what filler rod?  Will welding a dome soften the piston material too much?  I was figuring on 4043 alloy rod and a simple dome with a spark slot. 

Thanks and sorry if this is a dumb question.