No real problem. A magnitude usuall allows for an increase of factor 10 in the size (mass actually) of the target. So base (3+N) should concievably allow you to cause something to grow by a factor of 2^N in each direction, for a total mass increase of factor 8^N.
I don't see why not.
Now this is something very different.
You can create a container that makes everything inside it smaller without too much fuss, but bigger on the inside than on the outside?
That's an idea that crops up every once in a while, it's discussed here and here but tends to end up with the Merinita mystery of Glamour.