grain bed depths

Hi all,

I'm wanting to increase the batch size for my setup and have heaps of headroom in the MLT (55L) but I'm not sure whether I'll get problems with lautering if the grain bed is too deep - anyone had experience with what works? With a 20 litre (ish) batch the bed is about 4-5 inches deep - if I double that, will it reduce the efficiency and increase the changes of a stuck sparge or anything? I need bigger batches cos it just seems to disappear too quickly...