I don't think that the DiaCompe's will work. You really have two issues with those brakes: (1) the reversed bosses; and (2) the much narrower spacing of the bosses on the front.

As to problem #1, I mentioned that I already tried the Paul touring cantilevers, which are similar in design to the DiaCompe's in the sense that they don't use the bosses to anchor the return spring. The return spring tension on the Paul brakes is adjusted in the same way as it is on the DiaCompe's. That will solve Problem #1, and will give you a working rear brake. In fact, the Paul's worked fine on the rear, and I believe that the DiaCompe's will also.

The front is where the real problem lies. Those front bosses are spaced about 2cm closer together than most anything you will find. So, for the fronts, while the DiaCompe's will solve your first problem of not having to rely on the reversed bosses to anchor your spring, the second problem will result in the brake shoes not hitting the rims properly.

The few unique brake designs out there that can solve problem #1 cannot solve problem #2, and vice versa.

If you still have my e-mail or phone from our initial transaction, get in touch and I will try to help you - otherwise, pm me with your contact info through this forum. I did have those XT's that I gave you functioning perfectly with the dust caps in place.