Developing Kodak 400TX pushed to EI800

I started developing my B&W negatives from the Vietnam trip and I happen to have 2 rolls rated at EI800. In the Kodak documentation (Kodak F-4017) for the new Tri-X film, we're supposed to develop at the same time for EI800 as for EI400, because of "the films' exposure lattitude... Prints will show a slight loss in detail". So with this in mind, I started developing with Kodak's TMAX Developer at 21C at 1+4 dilution for 5 3/4 mins as in the spec sheet for EI400. The result was a little thin, which I assume was because of underdeveloping. The negatives seem a little light. I've not scanned it yet but I'm prepared for some additional photoshopping before the negatives are printable.

As a lesson, since developing for EI1600 is at 8 1/4 minutes, I think next time for EI800 I'll try something in the middle, say 7 mins at 21C.