Jim,
I think you are right, but I'm not sure that it will be able to do any twisting, the alu arm is very thick and wide ?
But, I will have a more experienced builder here look it over too, if it's no good, I will change it to clevises, thanks for the heads up !
(I have used the same method before on other large scale planes, 2.7m comp arf pitts S12, Eurosport, comparf 2.6m extra 300, and never seen a problem)