We are adding a plug in main lug kit. this is for a hotel we are rising up 4 floors. Each panel is fed in and out
If it is a plug on type "sub feed lug kit" then make sure your incoming feeder lands on the fixed main lugs and outgoing feeder lands on the plug on kit and you are fine.Hold down clip not needed then, it is treated just like a breaker. If it was backfeeding the panel, then yes, it would need a mechanical means to hold it in.