Thanks to you all for your thoughts.
Re: the stretch that allene mentioned, I'm using sta-set x in order to reduce stretch, and the portion of the line from the boom to the foredeck is Amsteel blue.
I will research more the effect of such a sharp, low-radius turn in the line before I make up my mind. The times this system will be put to hardest use will be to withstand a sudden and significant load from a back-winded 353 sq ft mainsail, so I guess the numbers will have to determine my course forward.
I've also seen that Colligo sells a similar part to Antal's that has a larger radius.
Thanks again for the help with this.
John V.