Socandyman, if you are not going to expose the stock to extremes, (let it lay in water for hours at a time, hammer/bang on the stock, etc.) the Tung oil alone will suffice.
It's reasonably water resistant on it's own, just wipe it down once inside if you get caught in the rain.
It doesn't take as much abuse as poly, but unless you are extremely tough on them it doesn't matter.
The nice thing is that you can renew or add to Tung oil by light sanding or buffing with steel wool then adding fresh coats of oil.
If poly ever needs refinishing you pretty much have to strip it and start over.
Plus, to me it usually is too shiny. It's generally easier to get a matte finish with Tung oil, or leave it shine if you want that look.
My hunting rifles that I've restocked or refinished are Tung oil finished.
I'm careful with them, but I do push through bush, hunt in the rain/sleet, keep them oiled, and wipe them down, etc. and they still look good.
For me the ease of renewing the finish outweighs the added protection given by the Poly.
The Ironwood stuff is a great product, I like the look, and I like the parts count addition.