I am 186cm tall and with the beachbar it is more comfortable and much better looking. I have no problem with my back since I exchanged the regular seat with the BMW R18 Roctane seat.
Today, I installed a Roctane seat on my Classic. It's looking great, is very comfortable and does support the back in a much better way compared to the original seat.
You're welcome. Happy to show you the detail. Don't forget to order the additional parts so you can attach the side bags properly. If you order the back rest with Wunderlich online, there you should get the information which parts you need. Wish you a nice weekend as well.