To be clear (and I hope I'm correct without digging too far back into the code), applying an adjustment OR overriding the value of a prize does NOT affect the calculation of other prizes with the exception of the leftover amount. When you change the value of the prize by adjustment or override, you will affect the leftover amount, so it is redistributed which will affect the value of those prizes. But only by the leftover amount. Their calculated percentage is not affected.
I can see how a conversion could help. I'll look into adding this feature in a future version. Looks pretty straightforward.
In the meantime, for final deals made I would suggest just using the Chop feature. Obviously this won't cover all scenarios, but for those final 2 or 3 players who make a deal, you can divvy up the prize money without affecting the prize values.