Adapter S52a to M48i – spacer ring for MPCC / Protective T-Ring

I have a Nikon D5300 and have been using the MPCC with an M42 t-ring. However, I would like to try to use the larger aperture of the M48 because the vignetting may be causing issues in some cases. Do you have an adapter that will attach a Nikon M48 ring to the MPCC with the correct back spacing? Or do you make a Nikon Protective T-Ring that works with this spacer?

Would this spacer (# 2458405) create the correct spacing for coupling a Baader MPCC III to an M48 t-ring? The M48 t-ring I own happens to be from Williams Optics, but measures the usual 11mm thick. I notice that when I thread the MPCC directly into this M48 t-ring, coma correction is not a good as when I use the M42 adapter on the MPCC and couple that to a standard M42 t-ring. Am I correct in assuming that this spacer increases the spacing for the M48 system to the correct 55mm? Thanks in advance.