How to implement bonding of multiple OpenVPN on ubuntu between 2 machines?

Question

openvpn

I'm trying to raise several vpn connections on 2 servers for fault tolerance and increase throughput
Idea: we raise N openvpn servers on one machine and N clients on another machine. On each machine, we glue the openvpn interfaces into 1 and do routing through the glued interface.
I looked here forums.openvpn.net and many more where. Connections between openvpn go up, but then nothing happens when gluing. At the same time, bounding also behaves differently on different versions of ubuntu 14/16/18
Perhaps someone has examples of ready-made configs and the sequence of raising such a connection?