it's not really a big deal IMO. back before I bought the CNC, we just did them the old fashioned way. the CNC makes it a little easier now.
when 440jim bought his Callies crank from me we discussed the option of opening the blocks mains so he wouldn't have to cut the journals on the crank. IMO and obviously Jim's as well, it was better to cut the block. i think the longevity of his engine as well as the performance speaks for itself.

machine shop owner and engine builder