That's very interesting
When installing the spreaders, you are supposed to have the mast laying guide down (this would allow the halyards to fall naturally towards the aft of the mast), the spreader bar is swept backwards to this tells me that there is going to be more room behind the spreader bar, also the mast should be swept backwards when stepped so this would be another demerit for placing, the halyards in front of the spreader bar.
So, halyards behind the spreader bar seems most appropriate. Have a look at the official setup guide for visuals of inserting the spreader bar.
https://u20classforum.org/Forum/index.php?action=dlattach;topic=899.0;attach=1189Where are yours?
-Josh