The detail of the gooseneck, slide, spring loaded locking pin and lines coming out of the boom. To me theie is no provision for the downhaul except to tie one of the lines off to a cleat on the mast.

1978 H27 Gooseneck assembly closeup

This photo shows the three sheaves plus the topping lift lifting point. (Currently shown as empty)since the Boomkicker is being used.

The center sheave is hidden, but the outhaul wire may be seen entering the boom

1978 H27 Kenyon boom and sheaves