Sure, move them. On my gaff cat boat I have them almost a foot to one side and about abeam of the aft tangent of the mast. Most gaff halyard attachments aloft are hanging blocks and there should be no lead problem unless you have a very odd set up. Mine land on a throughbolted eye and turn through a double block that has a long D shackle to allow enough height that the lead back to the cockpi clears the coach roof. You may need to install either a spring around the eye and shackle or a bit of semi-flexable tubing (nicely hidden in a leather sleave) to keep the assembly from clunking on the deck when the halyards are eased. Under tension the lead from the block to the eye will make a 45 degree slope so sometimes, depending on cabin location, there are clearance issues there.
Another alternative if you can get rid of the lead back to the cockpit would be to make a rail and belaying pins on the shrouds and come to that - a very nice thing.
It's not so odd to have the halyards come to cheek blocks on the mast that one expects trouble. Sometimes that little side push is aggrivated by the hoops sagging and binding. I have a tag line from the parrels on the gaff jaws that comes down the front (diametrically opposed to the site where the hoops are laced). It's set such that during the hoist, when the gaff is about horizontal and both halyards are being swayed up together, that line holds each hoop horizontal. Once the peak is pulled all the way up, the parells line sags down and thus slacks the whole tag line but that matters not at all. Keeps the hoops from binding on the mast.
G'luck
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