I just quoted wedding cake for 150 people. 6 inch square take home for bride & groom, 10 inch square and a 16 inch square. Do you think doing those measurements will look out of place beings they are not 6 inches difference in the top to tiers?
I don't necessarily think the sizes will look silly but you might want to check your serving sizes. If you are not planning to serve the top tier, I think you might only have 110 servings with the 10 and 16 inch square pans. You will have a lot of space one the corners but you could put some flowers or other decorations and it should look okay. Also you could offset the tiers rather than stacking them straight. Hope that helps.
According the the standard 1x2x4 serving size you should get 50 servings from the 10" and 128 from the 16" so you will have 178 servings from the bottom two tiers.
If you are concerned with the sizes you could always take the bottom tier to a 14" and have 98 servings. You'll only have 148 servings then, but leave that up to the bride on how many they want to pay for. That is at least a $75 difference by what I charge.
I did put on the contract what Wilton said the two bottom tiers served 178 and that I say it serves exactly 150. I was just concered that the difference in tiers was not exacty the same being it was 6 inchest between bottom and middle tier sizes and only 4 inches between the middle and top tier. will an extra inch on either side really make a big difference to the eye? Would it look weird if a trimmed a little of the top tier to make it like a 5 inch X 5 inch then there would only be about a 1/2 inch on each side which probably won't show too much. Opinions please.
Have you tried getting your pans out and stacking them up upside down? That would show you exactly the sizes you're looking at.