Just wanted to let y'all know that we installed a gate valve in our 305RE. It worked perfectly to equalize the grey tanks. Now I really do have a 90 gallon grey tank capacity!
Are the grey tanks in the 305RE at the same level? The kitchen tank (toward the rear) in my 369RL is higher (6"?) than the bathroom tank (next to and at the same level as the black tank) so I couldn't do this.