I'm just on with this now with my cheap Cyma V2 box. I've swapped out the piston from plastic teeth to full metal; same travel length although I did consider short stroking, but decided not to. I've swapped the stock piston head for one with a bearing, and swapped the plastic spring guide that has a single washer, for a steel spring guide with a bearing. I've not gained any preload as the original piston assembly had a solid steel inner that was 9.80mm. The bearings are both 4.56mm depth so that sorts that, I've gained a fully floating spring which should give it an easier life. Swapped the plastic nozzle that doesn't have an O-ring, for an ally one that does, now compression is excellent. I've polished the piston runners and tappet runner grooves and removed all the casting flake and radiused the large cylinder cutouts. I bought some solid bushings (SHS) to replace the factory ones that have the "X" cutouts, but the new bushings are a fair bit thinner so I won't bother. I was going to buy and use some Begadi bushings but the postage is stupid money. €8.90 for the 6 bushings, and €18.90 for the minimum postage!!! Feck That! So, just the shimming now then rewiring for perun and that'll do. I've already changed the bucking for a Silicone 50 degree Super Macaron seeing as winter is nearly here. I'm going to see if I can get hold of either Modify or the FPS bucking as per your previous recommendation.