If we're talking geometry I think you'd get the best leverage if the seat were
closer to the pedals but higher up...Stretch Cruisers can be hard to crank up hills since you can't really stand on the pedals
here's my stretch.
picture trying to stand up on the pedals and crank that. It's nearly impossible. Its a great bike for comfort and flats but the riding position is meant for comfort rather than performance.
This is Juggler's bike.
A bike like this you can stand on the pedals and power it up a hill, even with a banana seat. The Banana Seat puts you further back from the crank so you can stretch out your legs without having the seat jacked way up. You won't get as much power from your legs like this as you would with the seat over the crank and just jacked up to a comfortable height....but you'll look quite a bit cooler and IMO be more comfortable on the 'nanner.
Thats kind of the tradeoff with cruisers. You get to look cool and be comfortable as heck but you will trade off a noticeable amount of climbing ability and speed. and when you go from a regular cruiser to a stretch you trade off even more of that climbing ability.