Modifyworld and Worldguard

Hello,
I'm using Worldguard with PermissionsEx and PermissionsEx world permissions plugin Modifyworld.
When Worldguard and Modifyworld are both enabled, Modifyworld denies anyone but admin from placing and building blocks, even in plots where the user is an owner and the construct flag is set to true.
If I give ModifyWorld permissions to higher promotion levels (deny if for default, enable it for Member), then the higher levels can build in public places – I only want them to be able to build in designated plots.
If I disable ModifyWorld, the problem goes away, but then the default group can modify the world, when I'm trying to make it so they cannot break and build in public areas.
If I get rid of WorldGuard, all my permissions work again, but I clearly need WorldGuard, which is why I'm here.
Is there a way to get both plugins to work so that
- default players can hop on the server and walk around without being able to damage the server's creations, its roads, or otherwise.
- more dedicated players can still not damage public roads, but can build in designated plots.
?
Thanks.