Found the original geometry chart for your SystemSix here for reference:
https://vintagecannondale.com/year/2007/2007.pdf Geometry info is all the way at the end of the pdf. ...and blurry.
The missing info from that chart will be "stack". Assuming that you are on the 54, the stack of your current frame is no more than 55cm, likely closer to 54cm. 53.5 even? If your stem is currently slammed, or even minimally spaced, you will need to keep an eye on "stack". THIS is the true SIZE of the frame. You can't make it smaller! If you're OK with the 97.5 wheelbase, 58 F-C, and 5.6 trail, this shouldn't be terribly difficult to reproduce with your next purchase. All of this, again, assuming that you are currently on the 54cm.
https://vintagecannondale.com/year/2007/2007.pdf Geometry info is all the way at the end of the pdf. ...and blurry.
The missing info from that chart will be "stack". Assuming that you are on the 54, the stack of your current frame is no more than 55cm, likely closer to 54cm. 53.5 even? If your stem is currently slammed, or even minimally spaced, you will need to keep an eye on "stack". THIS is the true SIZE of the frame. You can't make it smaller! If you're OK with the 97.5 wheelbase, 58 F-C, and 5.6 trail, this shouldn't be terribly difficult to reproduce with your next purchase. All of this, again, assuming that you are currently on the 54cm.