Some Questions:
1) Is it right to assume a slotpitch of 2 inch?
(because you mentioned a net length of 50 inch and a "stub length" (means
slot pitch) of 2 inch.
How long are the stubs (traces from connector to receiver) on the plug in
boards ?
2) It is a straight bus, you have one plug-in-board at one slot, not two ?
Your schematic leaves the possible interpretation of two boards (one from
front, one from rear / or one left, one right, seen from
top). Or is it a main line with "trifurcations" at every slot, and each
"side branch" running to a memory module connector ?
Attention: the formatting of your mail may be changed on the "receiving"
screens !!! (an older powerpoint version sketch may help,
everybody should be able to read it!)