After some pondering in the garage, I think I've answered my own questions. The hinge with new springs does flop in that initial opening phase but so does the older sprung hinge. The latter just doesn't flop, it moves with coaxing. The new springs are thinner than the old ones, but the flopping is more a function of how precisely the oversized holes were bored in the hinge members. One set just happens to swing/pivot more easily than the other. Function should be fine. Thanks for reading my ramblings.
