I don't think this would be possible because there's an admin cost to propose a variation and it would be very difficult to make a compelling case given the very short timeline.
Hi Derek and welcome to the forum, with only 5 months to go it might be advisable to sail through it, it would take a while for a F&F to go through and you're almost there well done on getting there.
Have a word with your IP get their views on it? x
IVA final payment left the bank on the 26th January 2013...looking forward to a debt free future.
If there is a reason why you cannot make the payments as agreed creditors would look favourably on an early settlement. Otherwise they would expect the IVA to run the remaining five months.