I'd echo Dave's view. Alpha recently made up a larger crank pin for my M21 because, when dissembled, one flywheel taper was too loose. Their prices are fair, so I wouldn't want to gamble on a cheaper big end bearing.
There were some big ends around where the pin had been turned & not ground
These wore rapidly with the expected results
Considering that you generally do the crank bearings at the same time, it is a lot of work & money to cave a few quid.
Also considering the life span of a good big end they are dirt cheap.
I would have put in well over 200,000 miles on the big end that was in the bike when I got it and the bike had been the first owners daily ride for near 20 years .
