That is a 1 stop overexposure?
IMHO If I were using 11min @1+50 (as per digitaltruth) for 400, I'd go with 8 minutes @1+50 for 200

A quick search in google showed this:
Quote Originally Posted by
Chris Waller , aug 20, 2004; 04:41 a.m.
I used to shoot HP5 at 160 ASA and dev in Rodinal, 1:50, 20 C, 9 minutes. I downrated the film to reduce contrast (I was using a condenser head at that time). I have enlarged to 16x12 from 35mm negs and while grain was visible it was, as Lex noted, an attractive grain, very sharp and 'crystalline'. I have also shot 120 HP5, devved in Rodinal at 1:50 and obtained excellent results. For my own tastes I find that manufacturers' quoted development times give too much contrast.