vang requirements

Hi again,
The last bit of equipment yet to be attached on our DSI (circa 1963) is the boom vang.
Problem is the mast is just under 22 foot and it is (at that length is HAS to be) stepped on the cuddy top. While I can get the necessary (according to the vang I bought from D&R Marine) 22 inches on the boom to drill the first hole for the vang plate, there is only 17-18" of mast from cuddy to bottom of boom. That will definitely not allow for a 45 degree angle of vang to mast. It will have to be maybe half of that. Plus, the lower section of the mast is taken up by halyards & fittings so that they will interfere with the vang when the boom is not closed-hauled.
So, what is the minimum acceptable angle for the vang? And, how can the fittings and halyards (made fast) be avoided?
Good Luck! (I'm thinking of simply not using the vang at all.) Please don't tell me I need a new (longer) mast!
The last bit of equipment yet to be attached on our DSI (circa 1963) is the boom vang.
Problem is the mast is just under 22 foot and it is (at that length is HAS to be) stepped on the cuddy top. While I can get the necessary (according to the vang I bought from D&R Marine) 22 inches on the boom to drill the first hole for the vang plate, there is only 17-18" of mast from cuddy to bottom of boom. That will definitely not allow for a 45 degree angle of vang to mast. It will have to be maybe half of that. Plus, the lower section of the mast is taken up by halyards & fittings so that they will interfere with the vang when the boom is not closed-hauled.
So, what is the minimum acceptable angle for the vang? And, how can the fittings and halyards (made fast) be avoided?
Good Luck! (I'm thinking of simply not using the vang at all.) Please don't tell me I need a new (longer) mast!