Does anybody have experience with the M-40 variation on the widely-used Marianna 2624 rootstock?

I have been trying to find a good disease-resistant, semi-dwarf plum rootstock that can hold up to our horrible soil in the south lowlands of Eugene. Based on various internet sources, the M-40 looks to be the best of the bunch in terms of handling heavy, wet clay soils.

Does anyone have any direct experience with the M-40 that they could share? If so, where did you get it from? Do you recommend a good plum variety to go with it?