The only top coils I've used were the cheap Stardusts. They didn't seem to have any of the problems that the larger top-coils do, or had them pretty rarely. I've read a lot about the Vivi Novas, probably the most popular top coil clearo for big battery mods, and I kept seeing you had to tilt them and stuff more and more as the tank gets lower and lower. I found a great bottom coil clearo that I use with my ProVari and it's the best thing since sliced bread, IMO. No leaks, no dry hits, no flooding, no tilting, coil head cleaning/replacement maybe every couple weeks. They work great with 100% VG also, all you have to do is remove some of the wick which is super easy and takes 10 seconds. Fill and vape. YMMV.
I'd love to know specifically which bottom coil clearo you're using - it sounds great! We just got the Vivi (mini, using the 2.8 head at 4.0/4.2 on eGo Twist) and within 2 days the coils are trashed/black, and darkening/burning our juice. Sure, it's high VG juice...but two days? I am certainly NOT impressed - argh
Do tell! Do tell!