I have been fooling around trying to make an inexpensive adjustable table for the K40. It is not too easy to keep it cheap and usable! I have been basing it on a lift table design but this only gives about 2 inches of usable travel. An adjustable head would be a better option with that amount of limited travel. So the table is still a work in progress but the bed has been made. It is not any cheaper than the LightObject bed but was fun making. It consists of some c-channel aluminum, expanded metal and range filters.
When you say range filters, are you referring to range-hood filters? If so, I think it’s a great idea, although small parts will not be able to fall all the way through. So I’m 50/50 on it.