You should be figuring the # of servings by the industry standard of 1x2x4 - as shown in all the Wilton books/yearbooks etc. If the customer does not get all the servings in the cake style they pick out you can suggest adding a 'kitchen cake'. This usually is a sheet cake that is 4" tall but only iced (and maybe bordered) - not decorated. An 8x12 should give you 48 servings - more than enough to bring the #s more in line.
9/29/14 at 7:50pm