so just to clarify, you were previously runing the hub in modem mode with the deco acting as a router, and now you've reverted the hub to being a router and have put the deco into AP/Bridge mode?
This is a viable setup, though you should really disable the wifi broadcast from the hub so as to reduce interference in your house.. The deco won't "extend" the VM network, it will create it's own, but rather than act as a router too, it will just act as a wifi bridge/access point onto the network provided by the hub (so the hub will be doing DHCP, NAT etc.. the deco's just provide the wifi).