To get penn above flush with the base metal in the overhead positon on 10g sheet metal try this. Bevel the 2 pieces down to a knife edge. A 35+ deg bevel would be best to give you some room to work. Gap the joint to whatever size rod you are using. 1/8'' would be easiest. Now this might sound confusing, but you need to gap the end of your joint wider then the begining because it is going to close up on you as you get closer to the end. Lay the 1/8" rod in the gap and get comfy and start melting that filler rod. Only use enough heat to melt the rod and then just a bit more to get you some good tie in to the base material. This will require 2 passes in the overhead. The key is to get as comfortable as you can so you are real steady.
Or you can do it the way you've been doing it with a slightly bigger gap and really shove that rod up in there. Thats the tuff way. The last 2 XX in those classifications are for chemical composition of the rod. If you are using a rod with a -D2 on the end of it your going to have to be on your game to keep it from sucking back. It is a very runny or fluidy rod. Just run it as cold as you can and that you still tie into the base metal.
Or you could throw your teacher for a loop and butt them straight together and fuse them with no filler and no gap. Your going to need to slow down so you start to melt the back side. Don't get it to hot or go to slow or you will suck it back this way as well.
Did your teacher have you do any oxy-fuel welding before tig?