SIP/NAT problem on CUBE behind Meraki

Hello, I have a client with a Cisco UBE (2921 router) behind a Meraki.

It's a bit of a weird setup where the CUBE is the gateway for VOIP and DATA and static route forwards

So the Meraki is 192.168.100.2 and the CUBE is 192.168.100.1, the Meraki has a static route for the VOIP network (192.168.200.0) to the CUBE (192.168.100.1)

The solution was going to be to give the CUBE it's own IP with 1-to-1 NAT on the Meraki - but I'm a little confused how this alters the SIP headers, won't they still be showing the internal IP address?

I know the CUBE can do SIP inspection to alter SIP headers and change the internal IP to External, ie:

request ANY sip-header From modify "192.168.100.1" "1.2.3.4" request ANY sip-header Via modify "192.168.100.1" "1.2.3.4" request ANY sip-header Remote-Party-ID modify "192.168.100.1" "1.2.3.4" request ANY sip-header Contact modify "192.168.100.1" "1.2.3.4" response ANY sip-header Contact modify "192.168.100.1" "1.2.3.4" response ANY sip-header Remote-Party-ID modify "192.168.100.1" "1.2.3.4" request ANY sdp-header Audio-Connection-Info modify "192.168.100.1" "1.2.3.4" request ANY sdp-header Connection-Info modify "192.168.100.1" "1.2.3.4" request ANY sdp-header Session-Owner modify "192.168.100.1" "1.2.3.4" response ANY sdp-header Session-Owner modify "192.168.100.1" "1.2.3.4" response ANY sdp-header Connection-Info modify "192.168.100.1" "1.2.3.4" response ANY sdp-header Audio-Connection-Info modify "192.168.100.1" "1.2.3.4" request ANY sip-header Call-Info modify "192.168.100.1" "1.2.3.4" request ANY sip-header P-Asserted-Identity modify "192.168.100.1" "1.2.3.4" 

So I guess my question is, without ALG, will modifying SIP headers be required to do this with a Meraki?