Thanks guys, I think I'll go for
Lancers 2 squadrons of 9 figs = 18 Fig unit
Chasseurs 2 squadrons of 6figs + 4 Mamelukes = 16 Fig unit
Grenadiers 1 squadron of 10 Figs unit
This also allows for the different unit types to be taken into account ie, lancers , lights, and heavy cavalry.
Anyone know of a source for a good 25/28mm Mameluke figure ?