Thanks for the opinions on the shift length.
I do concur with scyth3. However, based on my previous assessment, I would also opine that having a greater risk versus reward ratio will attract more renters looking for a higher potential payout and will therefore increase the pool's average hashing rate.
Personally I agree. It seems pointless to gamble with a small jackpot and with the odds stacked against you (as they always are at casinos and when renting overpriced hashes). On the other hand, people do play the penny slots at casinos for hours. There must be some attraction to it.