However the B feels is just part of how multiple string basses feel after most of us came to them from fours. 35 or even 36-inch scale axes are an answer some players prefer. For me, the greater overall size and the smaller selection of strings made me decide to stay with a 34-inch scale.
I think this 'floppy-ness' business is overdone: For me, all five strings feel different in tension, just as previously all four strings felt different. I have two 34 fives, a Series-shaped Spoiler and an Elan.
I have lots of other concerns playing-wise that come before me splitting hairs about string tension !
As Mica said, there's lots of things that go into this, and it's very subjective. There's an adjustment period involved that involves way more than just 'gee my B-string sure feels loose'. For me, adding one string changed everything, and I couldn't wait to get away from fours as I wanted to play across the fingerboard more than up and down the fingerboard.
J o e y