Phew... Good to see some comma's migrating into your posts...
Anyhow mate, there are a few minor sags in the line from the sink but that's not going to be the cause of the shower flood I suspect flow has to go down, out the waste and then back up the shower line. The water takes the path of least resistance so it's more to do with the longer hoses and lack of fall from the waste pipe to the sullage. A couple of shorter section of hoses would work better I'm sure, but yeah I'm keen for something more reliable. Send through pics of the new set up mate as I love the screw on connector idea, much better than trying to force on the existing hoses...