I've got a Keeley made Cor3 and what I think is an SS MMi, the Cor3 is more usable for sure - by current trends it's not even a lot shorter than normal. The MMi does actually hit noticeably further than a normal bat though. My MMi is too light really (2lb7), I'd love to see the damage a slightly heavier one could do!
Got an MMI Premium that weighs in at around 2'10 or just under but not used it - may need to give it a net. Also have one from Trescothic I think - but that is heavier and I will have to see if I have it still, or whether I was dreaming that I had that one!!