Impressive. With the info you've given, here are a few thoughts. First off, you obviously are a big dude. Either pretty tall, like me or built like a brick shit house. If you're 305 with 15% bf, then that means you've only got 45 or so pounds of bf TOTAL. You've got a lot of mass. I would think that definitely is in your favor since muscle burns more calories. I suspect at that size with 15%, your diet is probably pretty close to spot on, considering your age (I know how that can be, I'm 40) and the fact that your metabolism has pobably slowed a bit. Also, at 40+ we all know that test levels are definitely not what they once were, unless you are on HRT. Having 10-12 cycles under your belt, I'm sure you've done more than just test every time, so you probably have a good idea of how your body responds to these compounds, since along the way, at some point, you've run them before. Also, you've probably put your system through a bit along the way.
My thoughts on that cycle? Probably overkill. If it were me, probably go with a little test (honestly) keep the HGH and add one other product. Maybe primo. At that weight and age (I am also 40+ and 300+) I am concerned about my bp, liver, heart, prostate, etc. and would rather be in it for the long haul, than risk my health. Also, absolutely, positively, check and double check to make sure that your diet is spot on, you get plenty of water and plenty of rest.
Just my thoughts.