First of all a joist pocket should follow some standard rules of thumb.
One is that the depth of the joist pocket shouldn't be greater than 5/8's the height of the girt. So, 5/8 x 11.5" = 7 3/16". Cutting a full 7.5" deep joist pocket exceeds this rule. I'd cut it 7" deep to leave 4.5" under the pocket for support. And modify the end of the joist to match by cutting away a curved slope from the 7.5" surface down to the 7" tenon.
As to how deep into the girt to cut the pocket, you should look at the load being carried by the joist and whether or not the 1" x 5.5" surface can support that load. 2" x 5.5" would be better and would most likely be ok, maybe not. Tough to call without knowing all the facts.
Granted that the joists aren't going to shrink any in length but the 8.5" girt is going to get narrower by at least 3/32" to 1/8" which will leave even less to hold up the load of the floor above, if there is a floor above.
And if you do use the FOHC beams it could distort more and move enough for a joist to drop out of a 1" floor joist pocket.
If it was me, I'd cut the joist as shown in the drawing on side B for the free of heart center beams.
But when inspecting girts for use you should look at the crown and make sure that it is up and then you can look at grain patterns for which face. If the girt is an outside wall girt then it will be carrying less load as it will only have joists on one side and then the joist pocket can be cut deeper into it.
If the girt has joists from both sides you'll need to review your design and check your load before you decide how deep into the girt your joist pockets should be cut.
Good luck with your project.
Jim Rogers
