All of my plate pants are longer than my base pants. I have a full break with room to spare on plate plants, not sure the exact measurement, but I'll agree, get them fitted with shins and plate shoes ON. Same with base pants, actually wear hour base shoes when fitting your base pants. I'll recommend adding about an inch or so to the fitting of the plate pants for the "riding up" factor. The best measurements are the ones that aren't actually measured, rather they are tailored to you.
Coming from working at Men's Wearhouse and seeing/doing a lot of tailoring myself now, it's best to actually have pants hemmed to where you want them, rather than go with a 30, 32, 34, etc pre-hemmed length like in jeans. Order Honigs pants unhemmed, I've heard they never come out just right.
My two cents: Buy unhemmed, take to professional tailor/seamstress, put shoes (and shins) on, have them mark them, sew them, and you should be good to go. Try them on before ever actually wearing them in case something isn't right. Also, ask them to leave 3" in the bottoms to ever have extra fabric available.