First cases, now trays

[Conquistador]

Pretty much have decided (fixated?) on Kaiser Rushforth cardboard cases for storage and short term transport of my miniatures (Legacy 25+mm, 15/18mm, 6mm, and 3mm.)

Now as to foam trays...

Much of my individual based figures are on 15mm circles (15/18/6/3mm,) 20mm circles (25+mm irregular, militia, smaller PCs,) 3/4" squares (25+mm drilled or disciplined regulars, average sized PCs,) with movement trays for grouping units on either LITKO movement trays, or one of the old Fantasy Rules! formats.

Indidually based 25+mm mounted troops default to 25mm x 50mm bases.

As I plan storage trays for shorter figures I am looking at KR "R" trays (20mm x 20mm slots) for foot troops, "N" trays (25mm x 50mm slots) for cavalry, "M" trays (25mm x 40mm slots) for doubling up foot figure or figures with long pole arms, and "F" trays (32mm x 52mm slots) for larger figures laid on their faces/sides) currently.

The point of all this digression is should I consider unit basing my 15/18/6/3mm mounted units on 25mm x 40mm bases since "M" trays make up the majority of my trays, keep them on 25mm x 50mm bases like my larger sized mount d units, or choose some other basing size?

It has been (seriously) suggested that I use 15mm x 30mm for heavy "cavalry" units, 20mm x 40mm for mediums, and 25mm x 50mm for lights for identification purposes by a primarily 28mm War gamer friend. 

Comments are requested.