I have searched on line and looked in back issues  of newsletters and can't find much information on setting the Streaker mainsheet traveler, the strop type on the rear deck, like Laser. 

The only information I can find is that the boom should be over the leeward corner of the boat and a bit slacker in light winds. I understand that single sails should not be as trimmed as close as a boat with a jib as the jib bends the air flow.

When I pull the main in it neatly sits at an angle, if I tack, pull the main in to the same tension the boom seams to at a different angle. I always appear to get a lot of variation in the boom position. Clearly there are a number of variables, strop length, main sheet tension and friction especially the strop block. Clearly five degrees difference in angle of incidence will have a big difference and speed and or heading. 

I watched videos of Tom Gillard and his boom seams to uniformly return to the same position on each tack but he does adjust the traveler to tune the boat.

Any options, guidance greatly received 

You might try the facebook group to get some more streaker relevant answers.