At least double the outside and i mean at least,i do these every now and again and there neck breakers.If there poly carb there easier than glass because with glass every mark will show up,a step ladder is also easier to use when cleaning these.If it was going to take me half a morning to do i would charge a whole morning and if was going to take me half a day i would charge a whole day if you see what i mean,if they argue about the price let them do it it`ll make them realise why you quoted what you did.