Picked up a RRA Large Pin 2-stage trigger cheap.  Wondering if expanding the holes on a DPMS Cast lower is a bad idea to install this trigger.

Any thoughts?

Bad idea.  Try trading for a small pin.

I agree... bad idea... why limit yourself like that?  I would think you can sell your RRA trigger and buy what you need...

I picked this trigger up from another member for $25 (Thanks Ray!).  In his post he explicitly inform the potential buyer that this particular trigger has malfunctioned numerous times in his lower.  I bought it as is, eventhough Ray expressed sincere interest in refunded my money if I can not get the trigger to work.  Deals a deal!  

My other option is to put it in a Camo-coated Cav Arms Lower.  Sonce I can not switch uppers, this is a dedicated lower.  Plus the polymer may be more forgiving.