#1. Im thinking you are asking about the length of 4" pipe for the Y' and X's, Thats 3 1/2" long, top side glued so there wont be any leaks at the drain, and the bottom half NOT glued so the unit will come apart.
#2.The X's and the one tee are just standard fittings,menards sell them for 4.99 last i bought, so the 4" pipe will snuggle fit in fittings, the S&D pipe 4"x10' is a belled end pipe, but youll have to cut that off and discard.
#3 yea, these are all misters and are 1 GPH misters.
Also: After your octagon is built, you'll need to light proof it, I wrapped a few with panda plastic and aluminium tape but didnt care for that so I bought some paint made for PVC , plastic , ect. its called FUSION , its a spray and a bit expensive because of the # of cans needed , Im going to check into auto paint with a additive for plastic for my next octagon.IN order to light proof I first painted the pipe black and then repainted white. I used corks to cover the mister holes and a 16 oz. beer glass for the 2 7/8" holes while painting the pipe, tring to get as little as possible inside the pipe.
The frame that holds up the octagon, I didnt glue any of the frame work but when i finnish with this grow I will be glueing just a few key points , but still be able to take it apart.
The feeder bar:
I used sch.40 pvc pipe, 3/4" but this is also going to be changed, with the 3/4" pvc I had to drill and tap holes, 1 hole between each of the 2 7/8" plant holes, so since 1 feed bar feeds 2 octagons 2 tapped holes will be needed between each of 2 7/8" plant holes.
with the new upcomming changes of the feed bar I'll be using 1/2" rolls of pipe , cut to length to build pretty much the same as the 3/4" feeder.The nice thing bout the rolled 1/2" tubing is ya just punch a hole and push in your take off in , much easier.
#2.The X's and the one tee are just standard fittings,menards sell them for 4.99 last i bought, so the 4" pipe will snuggle fit in fittings, the S&D pipe 4"x10' is a belled end pipe, but youll have to cut that off and discard.
#3 yea, these are all misters and are 1 GPH misters.
Also: After your octagon is built, you'll need to light proof it, I wrapped a few with panda plastic and aluminium tape but didnt care for that so I bought some paint made for PVC , plastic , ect. its called FUSION , its a spray and a bit expensive because of the # of cans needed , Im going to check into auto paint with a additive for plastic for my next octagon.IN order to light proof I first painted the pipe black and then repainted white. I used corks to cover the mister holes and a 16 oz. beer glass for the 2 7/8" holes while painting the pipe, tring to get as little as possible inside the pipe.
The frame that holds up the octagon, I didnt glue any of the frame work but when i finnish with this grow I will be glueing just a few key points , but still be able to take it apart.
The feeder bar:
I used sch.40 pvc pipe, 3/4" but this is also going to be changed, with the 3/4" pvc I had to drill and tap holes, 1 hole between each of the 2 7/8" plant holes, so since 1 feed bar feeds 2 octagons 2 tapped holes will be needed between each of 2 7/8" plant holes.
with the new upcomming changes of the feed bar I'll be using 1/2" rolls of pipe , cut to length to build pretty much the same as the 3/4" feeder.The nice thing bout the rolled 1/2" tubing is ya just punch a hole and push in your take off in , much easier.
things get a little "hazy" ...
cmon the fighter jet wasn't built in one try, but at least ya still get some pretty heavy nugs there. jah bless the HDF huh, i don't have any genetics even close to that size! well just wanted ta congratulate ya on another successful run, an sharin the tweaks n lessons ya learn, so we can appreciate your hard work too 
Can't imagine how much more you'll get with each tuning improvement to the system 
Nice job!
