The first part(bolded) is definitely reasonable. The second part is debatable.
First off, Guy and Lee both start out with Kurama's chakra, meaning that their attacks are gonna be:
-Much faster (as seen when Lee was able to kick Madara before he was able to react properly.)
and
-Much stronger (Lee kicked straight through Madara's body AND severed his link with the juubi in ONE kick)
Your arguement of them having no way to break it holds no water. Hirudora has a significant feat where it was able to at least force Madara to deactivate his complete susanoo(whether it was destroyed by the tech or it was deactivated due to madaras sudden lack of control from the blast has yet to be revealed.)
You also say its to high in the air, which I am guessing that you are referring to PS. People dont seem to realize that forming PS actually takes time to do. Not only does madara have to create the final form(with its massive size, legs, and clothing), but also stabilize the chakra, all of which didn't happen in one panel. In that amount of time, Guy and Lee would be able to pulverize whatever Madara has made while he is trying to form it, causing him to repeatedly waste his finite chakra trying to complete it.
If things got down and dirty, they are able to, by the statement of the OP, use the 8th gate once, consuming all of kuramas chakra to keep them alive for its duration. While featless, the 8th gate's power is hyped up so tremendously, that it is very possible that not even PS would likley stand up to a barrage of blows from it, let alone two 8 gate users.
It is much more likely that Madara will fall victim to chakra exhaustion before Lee and Guy, even with the EMS considering how much chakra it would take to maintain something as powerful as PS whereas both Guy and Lee have both been noted to have greats amounts of stamina naturally all of which is greatly supported by Kuramas chakra.
