In my implementation, knpkpbb is 372M, knpbkpbb is 1.6G , and knpekpbb is 2.4G. This is just to give you an idea. It could change with different implementations. In order to study the position in 4th floor, knpekpbb has to be built. Will it take time and disk space? Yes, it will. Is it a waste of time and disk space? It depends on how important Chinese chess is to you. ;-) Hard disks with capacity of 100-200G are readily available. It seems time it takes to build a database is more of a problem. Do you think it is worth the time and disk space or not?
The position on fourth floor is available:
http://206.171.116.227/cgi-bin/endgame.cgi?3BK43p55B36n291P79e895k3
And here is the position for the very top floor:
http://206.171.116.227/cgi-bin/endgame.cgi?4K43pB45B36n2996P294b45k3
For knpbkpbb, the following one could be more challenging:
http://206.171.116.227/cgi-bin/endgame.cgi?3n1B3p3K45B3995P393k1b399