I used to have problems with flooding when I didn't fill the carto first and when I used the grommet style tanks (chibi and sub tanks) But now I haven't had one instance of flooding in months. I punch my cartos with a hammer and long sharp screw. I mark where I want my hole, go outside on my porch steps (that are brick) place a dish towel on the bricks and place the carto on the dish towel, cradling it in the groove made when two bricks are mortored together (to better hold it in place) place the screw in the mark and a couple whacks and I have a nice hole. I leave the condom on while punching it to give a better grip.
Then I
condom fill the carto. If I feel I have overfilled the carto I just blow through it to clear the center tube. Then I assemble it in my dctank. Then I fill the tank by pushing the carto out a little and use a syringe to fill it instead of dripping down the side. fill down the side of the carto, not the middle! I pop the carto back in the tank and vape away. I always check my cartos with a multimeter before I even start punching, you never know when you're going to get a bad one that registers too low in resistance. Testing before you do anything will help ensure you don't damage your PV with a faulty carto. It's rare for me to get a faulty carto. I use the xxl boge 3ohm cartos and have only had one that didn't meter right. Since these cartos are long enough to fit in the dctanks, I don't have to do any cutting of the tank for it to fit.
If you are experiencing flooding, it's almost 100% because there is an air leak in the seals. A carto that has malformed due to punching could throw off the seal. I used to drill fill holes in my tanks but stopped. It is easy for them to not seal around the screw and leak. I have a friend who I mentor and gave her one of my tanks that had a fill hole. she said it kept flooding.. when I went to her house to see what was going on... I found that the screw in her tank wasn't tight and was letting in air.. I gave her a new tank without a fill hole and she has had no problems since. As for the grommet style tanks, the ones that use vinyl grommets, since they hold the carto in a death grip, you'd think that they would make a good seal but they don't, I had many instances where the grommets did let in air as I vaped and they are hard to syringe fill.
I use single coil cartos.. I never had any luck with dual coils, no matter what I did or how good the seals were, they all flooded. I got my tanks in my4jewel's co-op, they are polypropylene instead of polycarbonate and I've had no instances of cracking. But I don't use cinnamon or any flavor known the crack the polycarb tanks. she said that
liberty-flights sell the exact same dctanks that I have. The xxl boge cartos can be found at
crystalclearvaping, they come in 2 and 3 ohms.. they are wonderful!
If you like the filler style cartos like boge, carto tanks are awesome! My only problem is that with most juices, I start to taste a stale "filler" taste within a few days. I meter my cartos often, with a multimeter and my provari because I've found that as they age, they can change resistance (go up or down) and that greatly affects the vape, with a vv device, I can change voltage to compensate and get much more life out of the cartos. I too use 70/30% PG/VG mixes and haven't found any problems with one hole punched the way I punch them. My holes are larger than the ones that come prepunched. Many people believe that the size of the hole matters but I haven't seen that. As long as the hole isn't freakishly larger or super tiny, wicking shouldn't be an issue. Sometimes, the first day I use a new carto, if it acts like it doesn't want to wick well, if it acts like it's kinda dry, I just take some dry pulls (quick sucks on the carto without firing it) and it settles down and wicks properly.
I haven't read past the first page of this thread so I don't know what all advice you've been given. Hope I helped.