I wouldn't hessitate to use the 1/4". You want as little vibration as possibly when cutting aluminum etc. That weight/mass will absorb that. Don't set the machine on leveling castors. I used them on the my plasma but would not on a router. Here are some pics of the bottom of a base i am going to replace my 8020 base with(cnc router). Its 1/4" walled 2.5 x 2.5. Castor use is only for moving cnc.