Hi Skeet, excuse my 2 cents worth here. FD grow more slowly than P Trifoliate. I got a bad grafted citrus from (?) and the grafted citrus died leaving the P Tri rootsock growing shoots. I love it! It now has about 7 branches to graft onto.
I'd pinch it when small (I'm sure Joe will tell you same), & you will get more branching-- more to graft onto.
Also, if you have a plant with tri-f rootstock that has shoots growing out of rootstock...let it grow, & graft onto that too.