The difference between IBS/NBRSA scoring and UBR is that they are different - the intent of the OP was/is to have a sort of, "SUPER SHOOT" for score - already somewhat complicated by having two classes (Hunter/6x/10Lb., & VfS), which the way the IBS Nationals are [usually] conducted (TWO DAY event!), has lead to a major decline in Hunter/6x participation.
Faced with the choice of either shooting two guns, and TWO full rotations a day, most people opt for the easier VfS, as there is less equipment to move about, not to mention the easier aiming and handling of the 13.5 # rifles. I've experienced the two guns thing several times now, and will not do it again - I, and I believe most others, shoot for enjoyment, not a workout.
I am very opinionated, that the National Championships should be a one gun, one yardage per day affair. THE problem is akin to a parallel discussion on another thread - getting enough volunteers to operate a four, or more, day event, as as is the norm at the NBRSA score Championships. From my perspective, a properly conducted score event, featuring both formats (IBS/NBRSA & UBR), would need to be, at least, a six day event.
That said, I will again state, that, based upon personal experience, I have never felt handicapped, in any way, based upon caliber - I have either shot well, or, "stunk the place up", and I have won/placed/shown at the NBRSA National Championship level, opting to shoot with, "stuff that'll never work", against the mass of thirty caliber rivals. I have nothing against UBR, I simply believe, that regardless of format/target/discipline, winners win and losers whine . . .or, in other words, regardless of discipline, the dedicated will excel, and dominate.
Back to the OP, and, my intial primary concern: if attendance is limited, how will we motivate potential sponsors? I do believe this a worthy cause - we need to discuss and identify how to make it work. Fore example: should it be limited to VfS? ? ? Keep 'em ON the X! RG
P.S. Since I've been deprived of emoticons, please do not misinterpret my attempts @ facetious humor.