You shouldn't even have to break in a Delta Frost. With the lower harps, you need to focus the stream of air a bit more to get a good solid note by making a more "tee" or "key" sound.
Sounds like you've got the right harps. G's however require a little more effort at the bottom holes (not more brute power) You might want to take a look at some of Jon's vids on youtube where he shows how to "breathe" through the harp. You might need to use a little more air (compared to for example a C harp) but once you've got it down, you should be able to play the lower notes (and the bends) without too much effort/problems. (Jon is using a different key in his vids if I remember well, but that doesn't matter, the principle is the same) Hope this helps
I have (2) G harps. An SP20 and a Delta Frost. I have a little trouble with the lower notes on both harps. I can't seem to get them broken in. Any ideas?