I did a 4 day split following the HP mass principles:
Mon - Upper press
Tues - Upper press
Wed - NC
Thurs - Lower body
Fri - back and bi's
Sat - conditioning/sled work
As I am in a fat-loss phase, I didn't put on massive amounts of size, although I'm thicker up top, my delts are rounder, and my thighs are bigger. (measured them b4 and after) The extra sled work for legs, which I did as much as poss most certainly added mass, as well as leaned me out somewhat (even with less than perfect diet) I did this for 8 weeks. I made progress every week, and enjoyed the methods of increasing volume, which has really led to me being able to auto regulate my own training. I have now modified my training split to suit my own needs, but still applying the HP mass principles.
After changing my split somewhat and adding some of Thib's circuits to improve my conditioning - I'm going back to doing 3-4 hours Muay Thai next month, after a 8 week lay-off because of injury. Obviously training volume will decrease. I'm continuing to make progress, either adding weight or performing more work ( 6 circuits up to 8) Honestly, these new methods and ideas have made a difference in my training.
Physique /performance wise no doubt, but more in that I really enjoy every session - I'm totally motivated. (those NC workouts work a treat - I've found you need them less when doing the circuits as you get really 'amped up' when doing them. I have my powerdrive after and feel great)For me the eccentric-less work outs/sled work. I've been dragging my Muay Thai bag with TRX straps attached + weights on top. Staff + kids at the school I work at in Bangkok think I'm mental when they see my before and after school in the gym!!!
I do believe the whole HP mass thing was a little over hyped at times: 'get the same amazing results as Daryl'....Lets not mention all the juice he was on, and the fact that he had someone did is diet, trained him and all the works.
Sometimes new programs can over complicate things a little...Everyone is different. sticking to a program strictly written by someone else isn't always the best way to make progress...
Try it, see what happens, adapt it to your bodyshape, physical capabilities, finacial/time limitations etc. I'm no muscle monster and never really have been, (175lbs, about 10% bodyfat)as I'm really into my Muay Thai, but put on nearly 7 pounds and got leaner applying these new methods while training purely weights. I'm gonna get down to around 8% BF and use my increased strength to try and even the odds with these little thai dudes who kick my ass on a regular basis. These new ideas and methods have most certainly changed how I lift, and I will continue to use them as a tool to help me to achieve any specific goals I set myself.
Best of all it was FREEEEEEEE!!!! But lets face it, the fact I've spent almost $1000 over the last year on Biotest supps, I doubt anyone is out of pocket.