You can do as Vic has shown in his picture by tying a line to the lifting strap; thus shortening the lifting height. We found that lifting at the spreaders makes a pretty good balance point for the mast. Shortening the lifting point by 6' would seem to create a very "top heavy" situation
Don't know if it matters, but we have the thru bar mast modification for our spreaders which makes us a bit more confident in using the spreaders as a leverage point