dtr 125 , quest for more power

hello,

can't resist squeezing some more power from my 02 DTR 125, i've done the

usual derestrictions, trouble is I'm 18 stone, so the bike struggles a bit.

Has anyone

1) used a athena 170 kit, did it make much of a difference

2) Whats the max cc you can rebore the barrel to, what

difference did it make

3) Are there any other engines or top ends that will fit with little modification

4) Are there any mods you've tried, that made a difference

dieting is not an option.

thanks