I wouldn't drill a larger hole in the slide. I've played around a good bit with tuning CV carb's, and I've yet to find a better set-up than one with an unmolested slide. When you drill that hole out larger, the afr gets real crazy (much less controlled). From my experience, most of the time poor use of the "jet kits" can kill milage and actually hurt performance. Keep in mind, the CV stands for constaint velocity. Drilling a hole in the slide and using a lighter spring might make the carb sound like it's sucking air like a 4 barrel quadra-jet, but that doesn't mean that the velocity is still there.
Earlier this year I did some road tuning with a WEGO afr emter on my lowrider that has a cv carb on it (the larger 44mm though), and based on afr meter readings - the light spring with an unmolested slide had a much more eratic afr pattern at cruise than the stock spring with unmolested slide. I kept the lighter spring in it, because it brought my afr to the range I wanted to be in....but it definitely provides much less control on the slide than the stock spring.
I've done a good bit of road tuning by feel with my carb bikes, and one thing I noticed was tuning by seat of pants is very subjective. If you're going to tune that way, make sure you understand the signs of rich and lean....even that doesn't make up for a true afr reading by an afr meter. When I road tune carb bikes I base everything on feel and how the exhaust sounds (tone), and even then I've been wrong based on afr meter readings. I think it is very easy to mistake overly rich for not being rich enough when you are tuning a bike by feel, if you're not paying attention to what your engine is telling you.
hope this helps,