Seems you did a copy paste of my post
But I've made good progress in making rar2fs work with rclone. Be sure to mount rar2fs with the following flags: --seek-length=1.warmup
--seek-length=1 will just analyze the first rar file of the folder, this means way less polling as only part of one rar will be downloaded.
warmup will analyze all the rar files in the mount before you even try to list them. Even better it will use multiple threads (default 5) so it will be way faster.
Please note you need the last commit for this to work, as latest release (1.28 as of right now) doesn't include it yet.
Hope this helps anybody.