Chinese Mini-Lathe Carriage End-Stop!

So I have really getting back into using my Chinese Mini-Lathe (i.e. Harbor Freight / etc see more here: http://diy3dtech.com/mini-lathes/) and decided I need a Carriage End-Stop as I am making dies for my new desktop pneumatic mini-press (see more here: http://diy3dtech.com/200kg-pneumatic-punch-press-machine/). So I designed two version, one with and the other without the use of a spring retainer (if you're looking for springs, look here: https://amzn.to/2SFTJJV) and us common 1/4-20 bolts a