Carbon Tube Bicycle Frame with Fabric Layup Joints

After some research, the next frame construction I focused on was using off the shelf carbon tubes (from a supplier like RockWest here), and then joining them with carbon composite wraps at the junctions. This has been accomplished by many small builders like Glen's excellent write up at Back40, but the same method has also been worked into a profitable boutique manufacturing model at businesses like Calfee (tandem), Filament, and Parlee.

The basic construction process is described here at Filament's website:

1. Miter carbon tubes
2. Fit tubes tightly together in a precision frame jig
3. Bond tubes together
4. Fillet blend between tubes with a filler material
5. Cover/wrap fillet blends at tube joints with carbon composite, wet or pre-preg
6. De-bulk and cure composite
7. Sand smooth

This method seemed fairly straightforward to accomplish, and project costs would be reasonable. I was somewhat concerned the filleting could reduce the strength of the joint because the filler material is non-structural, and would limit the surface area where the composite joint can bond:

One of the most highly stressed regions of a bike frame would not have sounds inter-member structural continuity:

This could be avoided with careful formation of the fillet shape.

Also concerned of lack of shape control. how could I form the region from the seat tube to the bottom bracket using only tubes and a filler material?