I have been running B400 skids on my brushless Cx3 for over a year and love them. Those as well as the 250 canopy mod and the boom mod make this heli almost bulletproof. The other day I hit a power line out about 150ft away that I didn't see and it fell down well over 50ft. Skids still looked good. Plus most my flying is outside on grass. I hated the skinny anemic little skids out there I was trying before this. On Rc groups the 450 skid mod is pretty much a given if you have gone to 3s batterys.
One thing I do do on my 450 skid modded Cx's. I use 4.5 to 5mm cf rod for my skids.
14s 800 Triabolo/SHS 800Gob/ 2x 700Gobs/ 2x 600s/Dbl/bls Mcpx/DSS Skytech CP Coax/Sk720Blk/Gps/540 YGE/YEP/ MKS/Outrage/MIBL Herc/Gryphon/CPro/ Scorp/KDE/SHS/Tenax/Lynx/HeliOption/RcTek/Microheli