I first did a lift with arround 28 glass blocks when i realised it wasnt meant like 16x16. I then removed that and did a new lift
at the same position. I removed all signs and buttons when I created the new lift. Now, it replaces some blocks with glass in every floor, the lift doesnt work correclty and it says this in console:

2011-12-26 19:56:16 [SEVERE] Could not pass event REDSTONE_CHANGE to Lift
java.lang.NullPointerException
at net.croxis.plugins.lift.Elevator.isInShaftAtFloor(Elevator.java:169)
at net.croxis.plugins.lift.LiftRedstoneListener.onBlockRedstoneChange(LiftRedstoneListener.java:76)
at org.bukkit.plugin.java.JavaPluginLoader$38.execute(JavaPluginLoader.java:525)
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:58)
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:339)
at net.minecraft.server.BlockButton.interact(BlockButton.java:142)
at org.getspout.spout.block.mcblock.CustomBlock.interact(CustomBlock.java:323)
at net.minecraft.server.ItemInWorldManager.interact(ItemInWorldManager.java:275)
at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:593)
at net.minecraft.server.Packet15Place.a(SourceFile:39)
at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:93)
at org.getspout.spout.SpoutNetServerHandler.a(SpoutNetServerHandler.java:550)
at net.minecraft.server.NetworkListenThread.a(SourceFile:108)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:527)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:425)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)

we fixed it. we still had the bottom floor with 28 blocks ;D