Foma 400+Rodinal= not enough grain for ya??
I though Foma400 had a decent amount of grain even in D76. (for me)
Like a few say here, I bet Dektol gets you to where you wanna be.
I think Rodinal at a higher temp will help considering you already have that.
I haven't tried it myself but have heard on these boards if I'm not mistaken.