I am surprised at the number of people who are drilling fuel nipples, carb orifices etc in an attempt to solve carburation problems on GMS 47's.
Before doing this I suggest you try a simple test. Start the engine and run it at full throttle. After tuning it for max revs, OPEN the needle. If the engine slows it is TOO RICH. This means that you are getting more fuel than you could ever need and therfore there is absolutely nothing to be gained by drilling out nipples or the carb!
Similarly I see nothing to be gained by filing the end of the spray bar tube. Opening the idle needle will have Exactly the same effect without the disadvantage of moving the end of the tube away from where ot should be (in the centre of the carb throat)
In my experience (having sorted quite a few of these engines) the problems are almost entirely due to the idle needle setting. While the engine may well tolerate an incorrectly set idle needle AT IDLE, it will invariably lead to problems transitioning and in the mid and high throttle ranges.
In my earlier post on this subject I suggested that the gap between the end of the idle needle and the spray bar tube should be about .002 to .004in at full throttle. This is a good starting point and the needle may need adjusting slightly from there. Another good way of establishing a starting point for the idle needle is to attach a long piece of fuel tube to the carb so that you can blow through it. Close the throttle rotor on to a modelling pin and adjust the idle screw until you can just start to hear air escaping (with your ear close to the carb) when you blow. This should give a full throttle idle needle position just clear of the end of the spray bar tube.

My 47 has many many hours under it's belt and runs perfectly. It pulls a 12.25 x 3.75 APC at about 12500rpm on a Tower muffler, idles reliably at under 1600rpm and hasn't even coughed let alone quit in flight for a year. And all this from an engine that was misbehaving badly, had no power at all and I thought was beyond saving UNTIL I GOT THE IDLE SCREW ADJUSTED RIGHT. Remember that ALL I did was adjust the idle screw and it solved all the mid and full throttle problems!