I don't have any specifics for you, but I have the same questions about my Bene 323.
Its a fractional rig with split backstays, and is a pain to tune. There is no adjustment in the forestay ( profurl furler which never had any kind of a turnbuckle). It always seemed like it was too long. I bought a Loos gauge and use it to tension the upper and lower shrouds to keep the mast in column. after that I measure the side to side distances to the masthead with a measuring tape attached to the halyard and keep fine adjusting at the dock. I still go out and sail to continue to adjust slack out of the rig. I have been using the tension numbers recommended in the "cheat sheet" that came with the loos gauge. The backstay are a bear to adjust because each side has a double set of turnbuckles. I rather think that were made too short by the original rigger. Every time we step the mast, we have a devil of a time connecting them.
I still think my mast is raked too far back and would like to get some means of shortening the forestay. I have just a little bit more weather helm than i would really like.
The boat goes really well when I finally get everything as close as I can to the way I want it, but it takes a few days of flat water sailing to get there. Some day when I get rich, or eventually need to replace standing rigging, I'll get a professional rigger to work on it, change the furler, and change the backstay setup so that I can adjust it. Until then, it gives me something else to play with all sason long.