Wood car Side sill replacement

Does anyone here know of any restoration group who has successfully replaced the side sills of a wood narrow gauge car without having to tear the entire car apart ?
Obviously there are a lot of cars on the C&TS that are suffering weather related problems to their side sills. In my experience, the intermediates and center sills don't have this problem as much, but I see many box, stock, and the few passenger cars which probably should have these sill replaced.
The preference is a complete replacement; not spliced and not "sistered". The problem we see is that among other things, the end sills need to be removed, the bolsters disassembled, and basically the car needs to be hung in the air so it doesn't collapse when the structural integrity of the side trusses is removed.
The D&RGW cars were built so that they would only come apart in the opposite manner they were built; from the top down. We would like to find another way so a car doesn't need to be completely disassembled to replace frame members.
Theories are nice, but I want to see results !