Its hard to workout some of this stuff sometimes when there are no hard and fast rules or recommendations, its usually a give it a go and see what happens thing.
Its a bit like the drive side bearing that is meant to be a roller, I use ball bearings in mine and so far have not had a problem. The plunger A10 I had did 45,000 miles on the roller bearing in it and my current s/arm one has done 22,000 miles so far without a hitch and the bearing still feels like new. The reason I use a ball bearing is so I dont have any end float problems.