1. Which granulation of Pyrodex do you have?
If it's Pyrodex P then you may not even need a hot shot nipple because it will flow better into the flash channel than the RS. Just place the hammer on 1/2 cock before you ram so the air can flow out of the nipple during ramming.
2. Have you considered using magnum percussion caps? RWS and CCI make them.
3. There's a device called a nipple charger that will dribble some 4F black powder into a nipple for more certain ignition.
Both Treso and Pedersoli make one. --->>>
https://possibleshop.com/s-s-nipples.html
And--->>>
https://www.buffaloarms.com/treso-black-powder-nipple-charger-tre110640
4. Consider using a booster charge of black powder when loading, just drop the 5-10 grain booster charge into the muzzle before the main load.
Some folks simply top the main charge with black powder while it's still in the powder measure.
Any drilling of a standard nipple hole may allow hot gases to create additional blowback when the gun is fired.
You wouldn't want the blowback to reset the hammer and damage the lock.
They're expensive if not impossible to replace.
Extra blowback may also clog the hole with more residue as a result, who knows?
And we don't know what the caliber of the gun is or the size your loads will be.
I wonder if in some cases, opening the hole could actually weaken the flash.
It's probably easiest to try using magnum caps, and keep the nipple hole clean by frequently using a nipple pick.
Obviously if you were going to open up the hole, it would be by the smallest amount possible to minimize any potential complications.