I am not a big fan of changing a bow from a hunting bow to a 3D bow and then back to a hunting bow again. That is just much changing and not enough of getting to know your equipment for my taste.
If you want to keep your setup up a "hunting" setup and still shoot 3D, then do just that. I have seen a bunch of very good scores turned in by guys with a pure hunting setup. In fact, at local shoots, I would say guys with hunting setups turn in higher scores on average than those shooting “target” setups in the open class.
Fat shafts will give you a few extra points, but again you are planning on hunting with your bow this spring and do you really want to be swapping arrows around and changing sight settings and all that?
As far as what to buy to help get a few extra points out of your hunting setup, a good set of binos is key. It is amazing how much a good pair of glasses will help you on the 3D course. It is much easier to tell if a target is leaning forward or backwards, or to find a spot to focus on in the 12 or 11 ring.
However, the best thing you can do to start increasing your score in a hurry is to get good at judging yardage. This is what 3D is all about. You can take the best spot shooter in the world and if he not good at judging yardage, he won't be worth a crap on a 3D course. Take your range finder with you when you go shed hunting and start guessing yardage on everything you see.
There are several different ways to get good at judging yardage and if you do some more research, you will have a full day of reading on your hands. The magazine Tournament Archer almost always has a good article discussing different approaches to judging yardage. The simplest one and the one I use the most is to get one yardage that you know EVERY time. This yardage is different for everyone, for me it is 25 yards. That is how far my butt target is from my back door, which I see multiple times a day and have shot millions of arrows at. I would say I can get my 25 yard mark 99% of the time, once I have that it is much easier to judge a 37 yard target from my 25 yard mark that trying to judge the whole 37 yards. Also, as you are looking at your target, if you rock back and fourth slowly you will notice that whatever is exactly in the middle of you and your target will appear not to move side-to-side like everything else. Now all you have to do is judge how far that is and you then know how far the target is.
There is a bunch of ways you can cheat also to guess yardage, but you don’t want to be a cheater do you?
One other thing, if you plan on only shooting local club shoots that have no speed restrictions, then maybe try to tweek your arrow setup to allow you to shoot as fast as possible and still have a hunting setup. There is a big difference where you arrow impacts at when you are shooting 300fps rather than 280fps and you guess a 37 yard target at 33 yards.
Ok, so one more thing. If you are shooting a 3D course that is scoring ASA (low 12's) learn how to aim for that 12. If you aim for dead center 12 and miss your yardage short, you have a very good chance of ending up in the 8 or even the 5 depending on the target and how bad you miss the yardage. Try aiming for 12 o'clock on the 12 ring, if you miss short (depending on how short) you may drop into the 12, if miss long, you have a lot of 10 ring to save you. This is why IBO 11's (IMHO), which are center shots, are so much easier to shoot, more room for yardage errors. Shooting for ASA 12's can make or break you, but in most cases, they break me!!!!
Have fun, enjoy shooting and knowing that you are becoming a better archer for when it matters, November!!!!