Also, if you pay out extra coins for short rounds, you are in essence proposing a proportional payment method.
Yes basically. CPPSRB for long rounds, proportional in short rounds. I'll re-think that though. DGM is great mathematically, but I'm not sure about my ability to reasonably implement it and I'd also set the parameter to zero that accounts for operator variance, as I'm working on a pool for fun and not to pay miners out of my pocket like inevitably bankrupt PPS pools.
I do intend to pay all transaction fees to miners, but shares are only credited d/D of the base new block reward (without transaction fees). So the transaction fees are "extra" (fractional) coins to pay towards the backlog, or extra pay in short rounds. I wonder if the average transaction fees are enough to eliminate long-term expected negative buffers, though. I was a math minor in college ~18 years ago, but I don't retain anything useful compared to Meni.