Dave, there are dome top pistons for the twin cam 30. Arias make them 9.2:1 CR, they also make another slightly higher CR piston also but cant remember what it was.
Edit. Found the info.
p/n= AP332104
10.6cc dome top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 9.2-9.4
p/n= AP332105
13cc dome top
21mm pin
1.280" compression height
Only stocked in 0.20 thou oversize (86.5mm).
COMPRESSION RATIO 9.5-9.8