For what it's worth, here is 63 grains of RL-15.5 in once-fired R-P 35 Whelen (AI) brass, trickled through an 18" drop tube. It is very bulky.
[Linked Image from i.postimg.cc]
I loaded test charges of 61, 62, and 63 under the 225 NAB at 3.375" for a test this week. Will report after shooting on Wednesday.

Rex