Amazing; last week a friend told me that at 1600 it gives pretty small grain in DD-X (yes, seriously). I guess everybody has different tolerance levels for grain. If you use it at 200 in perceptol this means you want very small grain. Have you tried, by the way, using FP4 at ISO 250 and developing in undiluted D76, as an alternative? (of course, with a different contrast and shadow detail). I'm eager to test pushing FP4, there are people that push it even 5 stops!
HP5+ (135 and 120) in DD-X gives by far the largest grain, especially in comparison to Tetenal Ultrafin Plus (now discontinued), ID11, Microphen, or Ilfotec HC. It makes me wonder why Ilford recomends it as THE liquid developer for this particular film.
In my experience, HP5 works best with Ilfotec HC at 1+31, and I have been using this combo for a long time. DD-X works fine with 4x5' HP5, tray developed, as it gives easy to print negatives.
My experince in pushing FP4+ is limited to Tetenal Emofin, also recently discontinued, but similar to Diafine. Results were nice, but so are those obtainable with HP5 and diluted Perceptol - very nice tonality.