JBoles, that's an interesting option. Thanks for sharing. It's definitely a nice plus to not have the fiberglass drilled into (leakproofing and future modifications). This is the first time I've seen risers that tall. I wonder if risers that tall present a "shearing" risk (
https://en.wikipedia.org/wiki/Shear_stress): meaning the weight might present a side force that would break or bend the elbow of the riser. Because each riser connects across the van, it seems like that force might be well protected against. Rain gutters are strong, and basically should be able to hold up a very large amount of weight.
I wrote the seller to clarify what they mean by "This system can hold up 250-450lbs depending on where crossbar is positioned". Do they mean per crossbar? eg. 750 - 1350 lbs if there are three crossbars. I also wonder if there is an off-the-shelf rack that would fit nicely in the space these risers create (if you have any links (or companies) to share for off-the-shelf racks would love it). You're probably right, it would definitely not look as slick as an Aluminess rack. Could potentially be cheaper. If my math is right though, three of these would cost $840 before shipping/tax, once I add a $1000 rack to that (assuming I could get one with expanded aluminum), we're up to about $2k. That's with no ladder (my $3k quote includes a ladder) Cheaper than Aluminess, but because it'll look funky and might be a lot of work trying to make everything work, that $2k is starting to look not THAT competitive.