The “allowed host” on the client side is to put the networks in you would like to route to. If you want to use the VPN tunnel for your default route it’s when you use the 0.0.0.0/0

But if isn’t.

• start by putting metric units next to the SAE units in the labels
• Eventually people get used to the units and then you phase out the use of them.

All science and most of the mechanical engineering is done in metric already. If you have a car made in the last 20 years ask the fasteners are already metric. So it really isn’t that hard…

Maybe you could do port knocking to have the firewall open the port to that IP after you hit a series of ports in the proper sequence.