Just to put a different perspective on this.
If you are achieving consistent results, then you do not have a problem! Simply add a little more malt to give you the extra 3 points or so.
You are brewing to make yourself a nice beer, not to hit some predicted figures thrown up by BS software.
I use BeerSmith2, but basically for recipe design, and to keep a record of my brews. I don't use it for volumes for mashing or sparging etc. I mash, I drain, I sparge, and top up with water to hit 34 litres pre-boil. My OG into the fermenter is usually within 2 or so points from predicted, but it's consistency you are after.
If you still think you have a problem, look at your system to see if there is anywhere you can reduce losses. Then simply adjust your brewhouse % to give you your desired OG outcome.
edit: I agree with Screwtop about boil off %. Boil off is in reality not a % issue, but a volume issue. This is one of the weaknesses in BS software. It is dependent on the surface area of your kettle, boil intensity, and to a lesser degree ambient conditions such as temperature and humidity. For example, in the same kettle your boil off volume will be much the same, whether you start with say 20 litres or 30 litres, but the % will vary significantly.