Doublestrike sources and stacking question

[RS-Makk]

I'm trying to plan out a potential rogue build and have some questions about doublestrike

Which of the following will stack/not stack?

Epic Cutthroat SmallBlade (6%)
Epic Spare Hand (3%)
Opportunist (3%)
Grandmaster of Flowers 'Hail of Blows' (3%) - thinking it may be a nice 'twist' assuming I go shadowdancer

What are other potential sources of doublestrike for rogues?

[Rogann]

I have no clue bout stacking however id twist haste boost in LD tree so you save yourself 10 AP for racial pre's in august.

[threefeetunder]

I'm trying to plan out a potential rogue build and have some questions about doublestrike

Which of the following will stack/not stack?

Epic Cutthroat SmallBlade (6%)
Epic Spare Hand (3%)
Opportunist (3%)
Grandmaster of Flowers 'Hail of Blows' (3%) - thinking it may be a nice 'twist' assuming I go shadowdancer

What are other potential sources of doublestrike for rogues?

According to what I remember from a dev post on closed beta (i'll edit this with the link if I manage to find it), doublestrike generally stacks if it's untyped or typed differently, just like everything else (besides weird stuff like dodge) in the game, no special stacking rules. So opportunist, hail of blows and epic cutthroat smallblade should all stack for 12% doublestrike.

He did say that items that gave effect were basically the same effect on both items, so similar valued doublestrike items probably wouldn't stack, but he was vague on differently valued doublestrike items, so unsure if epic spare hand would stack with epic cutthroat smallblade.