[skropi]

First of all, getting really high speeds is easy to do with 9.5mm steel and a long draw. Your 115cm draw is ok, but consider extending a bit, lets say to about 125-130cm, and you'll see good speeds with very little draw weight.
Now, what is important is to establish a consistent technique, so practice at the draw length you enjoy the most, not the draw length you think would be more accurate.
For a 115cm draw length, a 0.60-0.70 thick latex, with an active length of 24.5cm, tapered 15/10 will be very fast. I would personally taper about 13/10.
In theory the most fps can be achieved with the thinnest possible elastic, as it will have the fastest retraction speed. But theory and practice is not exactly the same, although equally important.
If you really like speed, shoot 3/4 butterfly, it's a nice compromise between full butterfly, which is a bit fiddly for me, and the shorter draw lengths.

 

[skropi]

Thanks for answer skropi.

Can you open this halfbutterfly more to me.

"If you really like speed, shoot 3/4 butterfly, it's a nice compromise between full butterfly, which is a bit fiddly for me, and the shorter draw lengths."

Is my 115cm drawlenght considered as a half butterfly or more or less?

Half, 3/4 or full butterfly are relative terms. The actual draw length depends on the height of the individual.
Half butterfly is when one draws back approximately to the shoulder, full butterfly is when the pouch holding arm is fully extended backwards, and 3/4 butterfly is the middle ground between half and full butterfly.
Of course there is everything in between. I, for example, shoot none of the above, as I extend to almost full butterfly, but not quite reaching it. That's the most comfortable way for me to shoot, so that is what I practice.
Keep experimenting with different draw lengths and see what feels better!

 

[skropi]

Even a thick elastic can be made to work, just cut it narrow enough. 1mm Gzk is very powerful, and if I remember correctly I used a 10/8 taper with a short draw.
The good thing about elastics is that they are cheap!

 

[skropi]

Yep. It's very powerful. Kalevala told me to cut it 15/10 and it's very good like that with short draw. Maybe i try to cut it 13/8 and 26cm(10 inch) active lenght and see can i pull it 3/4 butterfly..

It's all about trying out what works. I made a lot of band sets till I settled in a setup I like. Just give each new setup enough time to get used to it, don't get in a hurry to change things up very fast!