What should I make?

It has come to that time when I can start working on a project. I have a lot of things that I want to do, but  only have time for one.

Options

- Improved bullpup with a writeup

- Expanded hornet tank with homemade shell (mostly pvc and some polycarb)

- UMB tank in a Longstrike or Firefly

- UMB tank and expanded hornet tank in a Longstrike or Firefly

- Crossbow overhaul

Which one should I do? Please let me know in the comments because I can't decide. 

Update

I know updates are really boring and no one reads them, but I think they are better than not posting at all. I am extremely busy right now and I have had no time for anything. I've been at school for 13 hours a day due to sports and other things and I have been overloaded with work. However, in a few weeks I will be on break and I will be able to work on some things that I have been wanting to work on. The first thing is an expanded hornet tank and the second is a UMB tank thing. I can't decide what I am going to do with these yet, but they are going well. I'm even considering putting them in the same blaster. Expect to see those finished in a few weeks.

I am also selling my Double Rainbow and Snapbow. The Double Rainbow is being sold for $80 (feel free to make offers though) and my Snapbow for $35-$40. They both work great and the Snapbow only needs the seal to be tightened. The Snapbow will not include the hopper or barrel. Let me know if you want a barrel or hopper with either of them. Just email me at Drev453@gmail.com, comment below, or pm "Drev" on NerfHaven if you are interested in either of these.