too much dead space, = too little sparge water = crap efficiency. Just make one out of cpvc if you wanna cheap out. I have a cpvc manifold and it works like a champ
I did make a copper ring with holes drilled in it and it is ok. Sometimes it gets stuck or get too much grain still coming through. At the moment I am doing batch sparges so not a problem for me but I am updating to a HERMS system and want to do it right.
If you desire an inexpensive false bottom perhaps you would be interested in a modified vegetable steamer the kind that collapses. I cut the feet and the center post and widened the hole and jammed a hose through it and it works great and it would accommodate a range of sizes. I considered putting one of those screens for a frying pan over it but it turned out it was unnecessary.
Midwest is having serious clearance on false bottoms just found this, if you want one there is probably very limited stock I would grab this you wont find cheaper for the real deal.