Are all white oak uppers A2 style? I'm starting with a RRA national match service rifle with removable handle (because it's nice to have options if the service rifle thing doesn't work out). If things go as planned I'd eventually get WOA upper as a replacement and have the RRA as a backup. The question is, is there much of an issue switching between A2 and A4 uppers with regards to sight alignment, cheek weld, etc? TIA