Well, I drilled a hole (smallest bit that I have with a pin vise - probably thinner than a regular safety pin) on my 2 piece 901 cart, on the bottom of the brown piece. 1st attempt was an utter failure, because I drilled the hole little too big. 2nd one was a little better - but the juice was still leaking out when I was refilling. I also tried to block the leakage by putting small Tbag filler on the bottom of the cup, but didn't do much either. Perhaps, 100% pg based liquid is too thin... maybe VG might be better for these hole mods, as they are thicker and less likely to run down.
Since I carry around the carts in my pocket shirts, I don't really want anything to leak out... so I had to toss them. It did hold more liquid w/o waiting time... but more important issue for me is the bounciness of the filler itself. Tea bags didn't work for me as it just gunked down... so I'm willing to find some pillow fillers for it, or fluval or what not.
It just seems like the cartridge filler life is just very short. If I get a day or two out of it, it seems like the filler loses its potential. Perhaps I'm burning little too much with my SD, but for me that's the definite case.
I don't mind topping off often, but only when I can get out some good hits out of it, maybe 10-20 times, not 4-5 times.

4 drops of juice really should do it, but for some great reason, it doesn't.
