You and the other person can't go into different menus (stamps,console,browse, anything) where Lua will not run. I can increase the timeout a bit if it becomes a big issue.
Also I just updated this, read the front post and the v1.0.4 changelog, I think you will like them.
EDIT: Updated again because I just realized I broke right click in that last update. All good now.
Hamachi is for those who can't forward their port.