Paul,

Well if Hebrew 6 shows that someone could lose their salvation, then it also shows that it would be impossible to get back:

Hebrews 6:4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,

The people that I know that teach that Hebrews 6 shows that we could lose our salvation, also teach that the sins would have to be really horrific to have this passage apply (i.e. they put the bar a little higher than themselves, to assure that the passage doesn't apply to them)

Gino