Also, for future image posting I suggest following this tutorial..
http://www.whitearmor.net/forum/tutorials/article/48-posting-images-in-threads-2015/
And good luck on the build.
It really depends on preference. I'd recommend trying the helmet pass suggested above as they aren't terribly expensive. I've also seen people use baseball helmet padding among a myriad of other setups.
Also note that there are different configurations of backpacks for TD, depending on what trooper your basing your costume on. Ant that the TDs in the special edition also a different style backpacks.
Excited to see this come together! And it will be nice for you to practice in this bucket before you get your other one. Before you know it you'll be a pro! <br><br>
Good luck! Feel free to ask any questions you may have.