Ok - so I called up Hennessy this morning and spoke to a very nice lady who told me that I could just send it back; but because I ordered/paid via telephone they'd have to cut me a cheque once they receive it back rather than just reversing the charges on my cc. Whatever - not a big deal. She also mentioned that they now have a version of the ULB with a zipper and no bottom opening. It's not on their website yet, but apparently it is available. She said that it adds "about an ounce" to the weight of the ULB, and to just let her know if I wanted one. I guess enough people were doing the zipper mod/asking for a top/side entry hammock to make it worth their while to add another option.
Not 30min later, Canada Post showed up with my Hennessy! I gotta say, that was extremely fast. I guess the warehouse must be in Vancouver... I refused the delivery and went and ordered the BB. Then I ordered an SPE, a MacCat Deluxe, and emailed Opie to change my Whoopie Slings from the HH specific ends to the normal way.
I guess I'm fully immersed now - in for a penny, in for a pound...