This isn't true crossbars so to speak but this is an inexpensive way to get two to three kayaks on the liberty. I thought I'd share it here.
Get four pool noodles.
Cut them to fit and trim the ends to slip under the side bars.
Install them evenly spaced
Load a boat or two and throw a pair of ratchet straps over the top of them and go.I use a rope loop around the side bars to hook the ratchet straps to.
$12.00 carrier from Dollar General.
Easy on and off too.
Hope someone can use this info. I know it's not for everyone.