The full pen joint that fltjwl is referring to would be something like the prequalified joint in D1.1 " B-L1a-F ", since you mention using core shield. 3/8" would be the max thickness and the root would also have to be 3/8". To do the same joint without a backing bar " B-L1b-F ", backgouging the second side would be necessary to achieve full pen and the fit-up dims change to 0" to an 1/8".
I've rambled too much without knowing what you are asking for, so i better stop,
John Wright