Good on you for staying within the realm of caution, and please continue to do so. I've built my tubes both inside and out of the purported limitations and have (knock on wood) yet to even vent a battery, but I noticed my single battery mechs struggling with builds I knew weren't undoubtedly safe. I enjoyed the vape I got from them, yes, but I found myself constantly wondering, and on a hit to hit basis mind you, how close I was to liftoff.
Take into account that I get a much more comfortable, comprehensive vape when I build well and within my CDR and it makes me question why so many out there push a single battery so hard. It's one battery. It's only capable of so much. And a good builder can provide themselves a blissful vape with a well executed coil or two.
If you're not getting enough out of a tube, get yourself a parallel. The same build on a tube will hit much, much harder with two batteries sharing the load, and you can build a shade lower without worry.
If that's not enough, get a series. Nothing rips like a series mech.
Don't get me wrong, I'm not a total fear monger, but you pet the dragon, you don't go balls first into the den.