Hi Gerdo
I hope the following helps:
When looking into silkaflex and other silicone/polyurethane mastics its difficult to get real data. Every ones mastic is the best.
I got this from Practical Boat Owner PBO magazine. But data as good as this is very rare.
Usually they test different types but never the one you want.
Check out
http://www.pbo.co.uk/gear/which-adhesive-sealant-is-best-20877Looks like the Sabatack 750XL is the one to go for but as you would think its not that easy to get in the UK
However Evostik is very very cheap
Also It uses a Houndsfield Tensometer just like the one when I did my engineering training.
Clive