Question On How To Properly Notate A Piano Thing...

So, this is what I have trouble with, the one bar:

And this is what it sounds like, and it sounds right:

http://www.impetus-aesthetica.com/pianoquestion.mp3

My question is what is the proper way to notate this?

No, I'm afraid that is totally confusing, this should work perfectly fine:

sometimes the tremolo lines may appear angled like this:

It works as sames as a trill but for larger intervals, it also specify the speed in number of dashes like semiquaver demisemiquaver etc.

I see, but it'll still be played as if 1/16th notes on each hand, staggered between left and right?

Also, how do you notate that in Finale 2010? Because what I'm really doing is 1/16th tremolo but having one hand 1/32 off from the other... if that makes sense?

Wait, I almost got it. This wonkey crap... I've got it cross-staff now. Took forever and a day to find it in Google search, glad I didn't go to their forums and ask just to have some elitist immediately shout "read the manual blah blah blah" (because it's not in there).

The question is how to get to where the tremolo beams are detached from the stems...

I would suggest using cross-staff beams - unfortunately I'm a Sibelius user and can't instruct you on how this is done in Finale, but the Sib method is to write all the dots in one staff and then instruct every other one to move to the lower staff. This will retain the beaming between notes whilst making it clear that the pitches are the be alternated between the hands. If this effect lasts for several bars my advice is to write out the first one as described above and use 'repeat bar' signs henceforth.