For those that may be interested, I was able to install a 122mm spindle with my Hollowgram SiSl2 cranks and XX1 32 tooth ring on my F29. It took some minors modifications but it all worked out.
In the picture below you can see I used a Leonardi Racing XX1 spider. The Cannondale spider will not work since it is curved bringing the chaining too close to the frame. The Leonardi spider is flat. If interested, the Leo spiders can be found at Dr. Cannondale.
Here you can see just how close the chainring is to the chainstay. There is only about 2-3 mm clearance. To get this clearance I needed to have the "lip" machined off the nondrve side of the spindle. This allowed me to move the spindle further out on the drive side since the lip was out of the way. This also allowed me to center the cranks properly. Otherwise, the crank on the drive side was closer to the chainstay than the nondrive side. Anyway, I wasn't comfortable machining the lip myself so I took it to a local machine shop and they did an amazing job for just $17.50
In these next two pictures you can see the clearance of the crank arms with the chainstay. There is plenty of clearance (3-4mm) and the arms are centered (same spacing on each side). There is also plently of clearance for my Stages Powermeter. Notice that the arms are tapered for the SiSl2. The other Hollowgrams are not tapered and would probably not clear the chainstay.
In this picture you can see where I added some carbon spacers to the nondrive side. This is needed since the lip was machined off. I couldn't find 30mm Inside Diameter spacers so I got some 1 1/8" and dremeled off some of the interior to widen to 30mm. Altogether I needed 13mm.
On the drive side, it is hard to see, but I needed 4mm of spacers plus the wavy washer. I found some Wheels Manufacturing 1mm BB30 spacers and used 4 of them.
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