My experience with gaff rigs are from larger boats than the previous post.
On these boats the upper throat block are attached to a "galow" so its located in plumb line above the block at the gaff throat when the gaff is set.
The best way to hoist the main sail these boats is to let the throat go up first - so while hoisting the angle between mast an gaff is opposit of when set, when throat is at correct hight just hoist on the peek halyard.
This is called to "let the peek drive the throat". On this kind of rig the peek halyard is fastend above the throat halyard on the mast.
If the throat hallyard goes thrugh a sheave in the mast you must have some distance between the throat and the sheave to avoid jamming.
Even with the setup I described you need some dsitance to get free movement of the gaff.
Two feet of mast above the throat is not much, are you shure it must be hoisted higher?
I found an article in Norwegian describing the gaff rig in detail, Ther are some drawings to look at http://www.ssca.no/Gaffelriggen_Knut_von_Trepka.pdf