I'm assuming the JD Barbeque Chunks you used were the same ones shown in earlier post and that you filtered through cotton wool to remove particles etc when finished soaking.

When I've used these JD Barbeque Chunks I did find that some bags were quite 'woody' while others were 'smokey' and when I found this I would empty the amount of chunks I wanted to use into a colander and rinse them with plenty of cold running water. This always got rid of any 'woody' problem

The proportions of chunks to spirit I recommended were what I found worked best for me so increasing/decreasing the ratio is up to yourself but I can't speak as to the results other than what I've posted in the past.
I also found the 'whiskey' could sometimes (not always) have a slightly smokey flavour but this mellows over time. I opened bottle last Sunday evening that was just 4 months old and there was no bad smokey flavour. Having said that, good Bourbon does have a feint smokey undertone so maybe I've just become accustomed to that taste.

I never drink shop-bought Bourbon or Sour Mash any more as I find it too sweet and lacking body.
I've experimented with Maple Syrup in this type of spirit because I found that on a rare occasion I got a batch off the chunks that lacked something in the mouthfeel. I put this down to the fact that we don't know if the chunks were from a barrel that contained premium Bourbon like Knob Creek or Booker Noe or if they came from a barrel of run-of-the-mill sour mash that would be used for blending.
In any case I would only add Maple - 2ml at a time in a 70cl bottle - then leave for 24 hours before tasting/adjusting further.
I have also used very small amounts of Maple to smooth out a spirit I intended to keep as sipping whiskey. Occasionally I've had a batch come off the JD Chunks that was exceptionally good - much better than JD - and this stuff I now bottle in 5lt DJs and leave to age. I currently have 3 aging like this and one got 25ml of Maple last Dec because the mouthfeel was not rounded enough while the others are like a premium Bourbon. Roll on the Summer when they'll get bottled and consumed with great gusto.

If your GF is mixing with Coke (sacrilege) she's not really going to notice the subtleties in a Sour Mash/Bourbon but Maple, along with Coke, would be far too sweet and I'm sure she's sweet enough.

Hope all this waffle helps.
AM
