Bruce,
Being that the Saito 100 and 125 are the same size because they use the same case (the way I understand it is that the 125 just uses a bigger cylinder) you can always switch them out if you need to. I still think something was goofy with you last plane or set up. Like I said, I have the exact same set up of plane and engine and it balances perfectly. Maybe do a dry run without fully installing the motor to see how she balances. The 125 on this bird might have you ripping the wings off and working for NASA as well. I'm sure it would work fine, but that is HUGE power for this bird. If you do go with the 125, promise us video! That baby might actually end up in orbit!!![X(][X(][X(]

-Jay