Iron Horse Root Beer Clone or something close?

I've been brewing all-grain for years but I'm brand new to sodas. I have in-laws who don't drink and I would love to start crafting root beer for them to drink when they come over. I would like to start with an extract and maybe use part brown sugar to sweeten. I'm not completely apposed to making the syrup from scratch but, I don't really have a trained pallet for root beer to craft a recipe for what I want. I do know Iron Horse is my favorite root beer and I would like to make something similar. Is there anyone here that has tried it and could point me in the right direction. Iron horse seems to have a very vanilla creamy feel to it. Maybe an extract with added vanilla and brown sugar for body?

It has been a year since you asked this question.
Did you come up with a solution?

oh wow yeah and another year since I saw this reply lol. Answer, no. I gave up on my root beer. Under the high psi for soda my perlick beer faucets were leaking and I didn't like the idea of needing to dedicate one beer line up for root beer. If I could make something like Iron Horse I probably would attempt the effort again, but I haven't found anything. I think Frosty's Vanilla root beer tastes similar. Makes me think the route to take is a cream soda root beer mix (not sure though)

Keep in mind, once you go root beer, you will never be able to use that line for beer.

You'll want to try several extracts to find one you like. As you know they all taste like root beer just not all the awesome flavor you want.

Maltodextrine is the key to that mouthfeel you want, I'm just not sure how much.

I run two of my taps for soda/seltzer only. I think the best thing to do is have about ~20-30ft of line for the soda kegs. I have a dual regulator and keep one for soda at 40psi. Alternatively you can split your primary regulator into a secondary and use the second one for beer at a lower psi. As far as flavor goes I use Accuflex Bev-Seal Ultra Barrier tubing which is glass lined and I have no carry-over.