Mount 40x40 Vrail onto C Beam Gantry Plate

I would like to mount the end of a 40x40 v rail onto the middle of a C beam Gantry plate
http://openbuildspartstore.com/c-beam-gantry-plate/

issue is. the 40x40 has 4 mounting holes. the Cbeam Plate has 2 useable in the middle
I cant tell if the middle square insert areas on the plate would accept a 40x40 Vrail