We haul bikes around a lot on our cruiser. My low tech solution is swim noodles with a cut the entire length of the noodle. Slip over rail, and secured with strips of bulk Velcro around swim noodle. I then stand up bicycles next to the rail, and use nylon webbing with male/female clips and snap and tighten bikes against rail (wheels on deck). I go around heavier taller parts of bike and secure to rail.
As a final thing, I bought 2 of the large padded wire tie things, I put one though a wheel if I can, secure to vertical rail if possible.
We’ve done this for 2 years with 2 adult and 2 child bicycles. Last year did 120 miles on a trip on the Mississippi with lots of big wakes and waves, no issues.
Only dislikes are black marks from tires on deck, and poor placement by me a few times caused bad visibility, but when I was more careful with placement worked great.
We get tons of comments and people saying they should do that, but have only run across a few people that do.
It’s great to get to a port and have a fun and fit way to get around!
Will post a pic later if I can find one.