Boas should NOT be fed the same way balls are. Every 5 days is too much. As mentioned, they have a slower metabolism. Your boa will do fine on a 10 day feeding schedule. You also do not want the rodent to leave a visible lump.
X2. 10 days is more than enough for a boa. Boas are not meant to be really thick snakes. Most people over feed and make them obese.