Maxing out signal strength on RT-AC5300/RT-AC68u/RT-AC68U mesh system.

[JCDinPGH]

I have a mesh system setup with a RT-AC5300 as my main access point and a RT-AC68U on each other floor. They are physically connected to the house gig ethernet and forced to use that as backhaul, instead of the second 5gz wifi. Because they shouldn't theoretically be using the second 5gz for backhaul, is it still necessary? Would disabling it boost my main 5gz at all? Anyone added bigger antennas? I have a large piece of property and I am looking to max out my signal strength. possible. The 2.4ghz connection spans a much larger area but is slower. FWIW, I have the asus merlin firmware installed and all nodes are using the latest non-beta as of this posting. 386 5_0. I even looked at outdoor wifi boosters but that seems iffy at best.
What can I do to boost my 5ghz signal? Upgrading my system isn't out of the question but trying not to spend more money on this system.

[mustangtom]

Your RT-AC68U nodes are only dual-band (as you probably know). Since you are using wired backhaul, then I would suggest making the RT-AC5300 5GHz-2 channel available as a second 5GHz channel, as it is not needed for the backhaul. Disabling the 5GHz-2 channel on the RT-AC5300 will not increase the power of the 5GHz-1, but it could avoid channel conflicts/overlap.

To cover a larger area, you could add more nodes. I don't have any experience with adding larger antennae. If you are trying to increase coverage outside on your property, then you may need to look at dedicated outside access points.