Nighthawk MR1100 slows when using as modem with google wifi

[rcraft]

I have a Nighthawk MR1100 with ATT where I can pull 100mbps down when hooked directly to my laptop.  I would like this to be a modem and hooked to my Google Wifi router, but when I do this the download speeds slow to 10-15mbps.  When I hook it up to google, I have turned off wifi.  I have also tried running it with IP Passthrough enabled and DHCP disabled (using the google for dhcp).  All of these configurations have the same result... it connects, but way slower.

Any suggestions?