So, the /29 is for internal hosts that need to be accessed by the outside world? You can create the /29 subnet on the LAN side of the MX. Then create 1 to 1 NAT rules using the same real IP in both the Public and LAN IP spots. Screenshot examples below. And apologies if I misinterpreted your goal.
Or if the inside hosts will have private IPs then just adjust from the screenshot below to have the real/Public IP map to the corresponding private IP.
![Screen Shot 2022-03-09 at 12.08.34.png Screen Shot 2022-03-09 at 12.08.34.png](https://community.meraki.com/t5/image/serverpage/image-id/22223i39734E5F8F94BB2E/image-size/large?v=v2&px=999)
![Screen Shot 2022-03-09 at 12.09.25.png Screen Shot 2022-03-09 at 12.09.25.png](https://community.meraki.com/t5/image/serverpage/image-id/22224i9FA00B782975747D/image-size/large?v=v2&px=999)