Tank Sunroof Conversion Bit

This is my very first attempt at 3d modeling, so bear with me folks.

I printed out [Da5id's tank](http://www.thingiverse.com/thing:266352) as my very first print awhile ago, and I love it very much. I love the community here and I really want to try and give back. I was thinking about my tank dudes trying to pick up people in their tank, and then I realized they might be able to pick even MORE people in their tank if they had a sunroof. So BAM! Now you can have your tank.

I would like to g