I use an rba Plus V1 in my toptank for high VG juices and it works well. Except i need to bottom fill it, otherwise there's not enough vacuum so it will leak. This pretty much defies the whole purpose (top-filling) of purchasing this tank for me.
Depending on your coil-build and power you use, the RBA that came with the toptank might not wick enough juice. Here's an overview of the different versions RBA's (5 already), the RBA Plus V1 works best for me: KangerTech SUBTANK Mini
Depending on your coil-build and power you use, the RBA that came with the toptank might not wick enough juice. Here's an overview of the different versions RBA's (5 already), the RBA Plus V1 works best for me: KangerTech SUBTANK Mini