speedstream 5100 DSl modem and routerboard

I have a dynamic DSL system and 2.9.45.
The modem has the PPP client built in and connects OK.
The ethernet interface can pass the public IP though or have 192.168.0.1/16.
It does dhcp but only gives one address, 192.168.1.64/16, even if the interface is set to pass the public IP through.
I’ve read on a dsl forum that any host with a 192.168.0.0/16 address can access the public side, and verified this by setting my PC’s gateway to 192.168.0.1.

My private network is 192.168.0.0/24, the Mikrotik is .03, and from what I see I can’t have my private and public interfaces both on 192.168.0.0, the default gateway wants to use the private interface.
Trying to add a static gateway with the public IP shows “interface unknown”.

I don’t have a public IP to assign to my interface
I don’t want to change my internal 192.168.0.0 network.

I haven’t used bridges so I don’t know if that will help, or if there are some routing rules I can use to make this work.
I’ve tried setting the public and private interfaces to proxy-arp but that didn’t help.

any ideas?

192.168.0.0/24, 192.168.1.0/24 networks are inside big 192.168.0.0/16 subnet.
You will not be able to use 192.168.x.0 subnet on the other interface unless public subnet address is 192.168.0.0/16