Ok I got the new Si hollowgram cranks installed with the new 109mm spindle. Here is how I installed them to give the clearance that I was happy with and have the cranks spin without binding on the bearings.

1. Put new bearings in since taking out the old sometimes damges the bearing.
2. put the new axel in with the directions on the axel (drive side specific since bulges are there for the bearings to sit on)
3. I evened out the axel which puts it in the right place.
4. (Drive side) Bearing shield, 1 plastic spacer, wavy washer, 2 plastic spacers then spider with crank.
5 (Non drive side) Thick aluminum spacer/bearing shield from Carbon Si cranks, 3 2.5mm sram spacers, crank arm.

I will note that with this setup on the drive side the wavy washer is not flat but compressed which keeps the bearings from binding. So far I have ridden 100 miles with them. Tommorrow will be a better test since I had 2 too many plastic spacers on the drive side last week which caused the bearings to bind. The only downside to this setup for other peaople is getting the thick spacer from the carbon cranks if you don't already have them.

With the 109mm spindle, Cannondale moves the wavy washer to the left side, as there is no more built-in shoulder. It is supposed to use a small spacer, maybe 2mm in width, on the right side. On the left should be a much wider spacer, maybe about 8 or 9 mm. Just counting the spacers you have currently on the right side, it seems like you ended up in the right place on your own. Main reason for the wavy washer to move to the left is for repeatability in chainline.

Thanks now you had me look back and I was incorrect on install. Yes the wavy washer should be on the left. The only way I was able to make it work without the thick spacer from the press fit bottom bracket assembly was to use the silver spacer from the carbon si cranks which is about 8mm. Since that spacer is essentially a thick bearing shield I guess I forgot to put the wavy washer on that side instead. I could swap it to the other side but I am going to see how it goes after tomorrow since everything is working so well now.

Readusted today per your instructions and now it is solid.

Update on mine, I'm going to pull the cranks and reinstall with the standard axle, and (probably) the standard bearing shield.

I cannot get the front mech (7970) to work correctly now- it won't shift up consistently.

Previously when the cranks were more centred the front shifted perfectly- ironic really, as I shifted the cranks over in an effort to improve the shifting performance!

Moving them back will remove the concerns about the NDS crank being ~1mm from the chainstay.