+1 to other way around. FOr a full boil, you actually want to use less hops than you would in a partial boil. You get much better hop utilization so you don't need as many hops as you do in partial.
I use beersmith to adjust my hops down to the original IBU's. There are some free online calculators as well. If you need a rundown, let us know, we would be happy to help.