Okay great thanks!
Regarding the pit fermentation, clearly it has survived in parts of the Caribbean but also was being used in America and Britain circa 1830 (John more grist ahem for the mill regarding the connections between rum and whiskey!). I do not recall the procedure being described in M'Harry's Practical Distiller (1809), perhaps in his part of PA the switch had been made to wooden fermenting vessels.
Delighted to hear that the 1830 account otherwise is close to your own practice. This suggests to me that your distillates, if made from 80% rye, should be close to early rye whiskey, and if aged more than 2 years (ultimately) in new charred wood, to Monongahela rye whiskey.
It may sound odd but I have a feeling the 1830 pit mashes probably were not weird-tasting. They probably had a high acid level (low Ph) to prevent any real spoilage - adding backset as you do today, and as James Crow did at approximately the same time, was likely another way, maybe more predictable, to get to the same result. The fact of certain plants growing near the sugar wash pits probably helped ensure a naturally good ferment, and no doubt something similar would have occurred for the mashes used to make these old barley and rye whiskeys. An equilibrium of some kind must have resulted, like e.g., the Ph in Flanders sour beer ensures its stability without strong hopping.
Gary
P.S. That said, it is true probably that the fermented sugar wash or dunder in the pits and new distilled rum made from them had a pungent aroma, I know that because I have some Jamaican Wray & Nephew white overproof which smells like that. (All new Caribbean rum does in my experience). It isn't a putrid smell of course, just a pungent, grassy-like scent. I guess this character is needed to ensure the rum will have the qualities traditionally associated after full aging. Maybe the 1830-era pits to ferment a mash for whiskey were somewhat similar in character, tart and sourish perhaps. In fact, even a modern distillery mash can taste like that. I have a feeling that probably things haven't changed all that much in mash production for bourbon or rye since 1830...