A large part of the reason for the size of the farrier floats is due to the need to fold and trailer the boats. I understand the theory about them perhaps not being bigger for safety reasons, but seems like an odd argument to me. Smaller so they bury quicker and risk instability early as opposed to instability later? I am not a designer so I can't say much more.
I sailed on a Multi23 the other day and the floats on it were more substantial than on the corsairs. They did not bury nearly as quickly as on corsairs. That being said, the wind wasn't crazy. The owner has experience on a sprint750 and he says the floats on the multi23 are much better for pushing things further. The trade off is that there is no folding system on the multi23 so the set up/take down part of the deal is much more labor intensive going from trailer to water and back.