I use my homegrown hops a LOT, almost exclusively for BITTERING. Mine have an approximate alpha acid value near the middle of the normal range. They are typically about 21-23% moisture when harvested, occasionally as low as 20% or as high as 25%, but about 22% is typical. As such...
IF using undried hops, you'll want to use about 4.5 times as much as dried ones.
If you normally use pellet hops and are concerned about the difference between pellets and whole hop cones, then the OP is right, you'll want to use about an extra 10%, approximately, to account for that.
I don't see use of homegrowns for bittering as a novelty thing. I see it as being very resourceful. I don't have to buy a lot of hops anymore, even for bittering.