Blackjack Variant: Blackjack 52

I've seen this pop up a few places, and am wondering what the house edge is on this game. Here are the main differences from a standard blackjack game:

1) Blackjack pays 1 to 1
2) Blackjack in Diamonds pays 2 to 1
3) 5 Cards or more totaling 21 pays 2 to 1 (not applicable after doubling)
4) 6 Cards totaling 20 or less pays 1 to 1 (not applicable after doubling)
5) Dealer checks for blackjack with A or T showing
6) Player blackjack always wins
7) Player may surrender late with any number of cards, after hitting, splitting, doubling
8) Player may split up to three times (including As)
9) Player may double down on any two or more cards, including after splitting and hitting (including aces)

Some questions I have about the rules that I have not yet had clarified:

1) # of decks
2) Can you hit split aces? (or just double)

So, what is the house edge here with perfect (non-comp-dependent) strategy? (And, as importantly, what is that strategy?)

PS: I should note there is also a sidebet that pays 300 to 1 if player gets a Diamond Blackjack. I think the house edge here is 9 to 12%, depending on # of decks. But, the game can be played without the sidebet.

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Quote: Ibeatyouraces

Look up Superfun 21

Ah, thank you.