Just so people know. Yes, the expected payout over the lifetime of a jacks or better game is 99.54% on perfect play. BUT, this only applies if you play with the full 5 credits. On 1-4 the payout is dropped down to about 98.18% based on the following info
1-4 credit bet
Hand Payoff Combinations Probability Return
Royal flush 250 493512264 0.00002476 0.00619000
Straight flush 50 2178883296 0.00010931 0.00546545
Four of a kind 25 47093167764 0.00236255 0.05906364
Full house 9 229475482596 0.01151221 0.10360987
Flush 6 219554786160 0.01101451 0.06608707
Straight 4 223837565784 0.01122937 0.04491747
Three of a kind 3 1484003070324 0.07444870 0.22334610
Two pair 2 2576946164148 0.12927890 0.25855780
Pair 1 4277372890968 0.21458503 0.21458503
Nothing 0 10872274993896 0.54543467 0
Total 19933230517200 1 0.98182243
5 credit bet
Hand Payoff Combinations Probability Return
Royal flush 800 493512264 0.00002476 0.01980661
Straight flush 50 2178883296 0.00010931 0.00546545
Four of a kind 25 47093167764 0.00236255 0.05906364
Full house 9 229475482596 0.01151221 0.10360987
Flush 6 219554786160 0.01101451 0.06608707
Straight 4 223837565784 0.01122937 0.04491747
Three of a kind 3 1484003070324 0.07444870 0.22334610
Two pair 2 2576946164148 0.12927890 0.25855780
Pair 1 4277372890968 0.21458503 0.21458503
Nothing 0 10872274993896 0.54543467 0
Total 19933230517200 1 0.99543904
This is using perfect strategy. Simple strategy will cost you about .08% return, but is MUCH easier to memorize and do on the fly without constantly referring to charts.
As far as the double up round goes. The odds are.
Double 46.15%
Nothing 46.15%
Push 7.7%
The simple strategy I follow is directly from Wizard of Odds
Four of a kind, straight flush, royal flush
4 to a royal flush
Three of a kind, straight, flush, full house
4 to a straight flush
Two pair
High pair
3 to a royal flush
4 to a flush
Low pair
4 to an outside straight
2 suited high cards
3 to a straight flush
2 unsuited high cards (if more than 2 then pick the lowest 2)
Suited 10/J, 10/Q, or 10/K
One high card
Discard everything
Play the highest you have up the chain.
Assume you have Ac 3c 5c Js Jc
Conventional wisdom would tell you to hold the 4 clubs and shoot for the flush, but the odds tell you to keep the 2 Jacks and discard the rest.
Edit: My only concern. There is NO independent audit of the code or safety procedure in place to discount any shenanigans that the site operator COULD pull to make it more profitable. I am NOT saying that the game is rigged in any way, I am just stating that it COULD be and there is no good way to tell, so you must trust the operator before you play.