Okay, so I have decided to upgrade my “gen 1” MPCNC to the new 525 parts as well as the new T8 lead screw. My question is, would a solid 5mm-8mm coupler (such as this one - https://www.amazon.com/Wangdd22-Coupling-Coupler-Alumlnum-Casing/dp/B01M8QXY8N/ref=sr_1_3?ie=UTF8&qid=1496847028&sr=8-3&keywords=5mm+to+8mm+coupler) work better? Being solid wouldn’t it remove any and all flex in the Z-axis?
They could, the reason I do not like those particular ones is the location of the set screws. They were made with the screws directly across from each other (cheapest way to make them). Ideal is a 90 degree separation. across from each other can cause misalignment and poor grip.
Interesting. Did not realize the position of the set screws could be a problem. I will keep looking then.
Honestly, would love something like this https://www.amazon.com/Anycubic-Stepper-Integrated-Router-Printer/dp/B019TRKAPO/ref=sr_1_1?ie=UTF8&qid=1496855422&sr=8-1&keywords=stepper+motor+lead+screw . I know the new Prusa MK2’s have had great success with leadscrew integrated into the stepper.
my pineapple coupler split/cracked into two pieces and ended up making my z axis screw up (a lot).
I printed a new coupler, but would be very interested in a better solution than the printed coupler. (not using the T8 (yet) though).
Print it in petg. It’s a little tougher than pla.
Forge it in aluminum, it’s a little tougher than PETG. 
I had issues with my pineapple coupler early on. I then ordered an alu coupler online, but instead of waiting I used braided hose, and some clamps as a quick fix. Works a charm! Still haven’t changed over to the alu coupler even though it arrived a long time ago.
Don’t mind if I bring this full circle, do you? ??
https://vicious1-com.myshopify.com/collections/parts/products/5mm-to-8mm-flex-coupler
Okay, so I decided to pick up one of these (https://www.amazon.com/gp/product/B01DVD87Q6/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) this week. Is there anything different I need to do in the assembly to account for it should I choose to use it?
I don’t think so, let us know how it works.
I will.