The radial arm flap depends partly on the size of your arm. My GP in my home state had two patients. Myself and another guy. Mine turned out at 4 1/2, while they other guy turned out at 6".
Since then I have seen some articles stating that the radial arm flap is less effective as it does not contain muscle and tends to wind up being more flaccid. Since I can't exactly go up to another guy and say lets see yours, I don't know what other's look like.
The flap from the side includes some muscle, and one Dr. gives a choice of 5" or 7". Although the larger size would make intercourse easier and its tempting to go for the larger size, I always wondered if it caused any problems as far as fitting it into your pants.
sam1234