do You have a schema ? do You have a manual ? If You do not find the missing piece: We should have the schema - and the manual would be very helpful. We can guess "Player-Unit of Super Straight" is identical to "Player Unit Faces" - we could use the schema "Faces" - a big problem are "Wire-Colors""Super Straight <-> Faces".
Sonic pins are "clones" of Williams - the used Williams Parts. You could try to get a spare "Player Unit of a fairly modern Williams pin" - or maybe just the missing piece (asking in pinside).
For documentation -> here: http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1977-1978/index.html#/8/zoomed and http://www.planetarypinball.com/reference/partsmanuals/WMS_Parts_1977-1978/index.html#/11/zoomed - no help.
A new topic with a picture "pieces of the Player Unit I have - can you help me getting a replacement part" - do You see on ...-page-8 / -11 the missing part -> maybe asking PBR ? (telling them the Part-Number)
If You cannot get the part: Mounting the two bakelite plates on a "spare Williams Unit" - a lot of work - but with schema and manual You can get the alignment.
No spare part AND no spare Wms-Unit: You can make your pin to be an "ONLY-SINGLE-Player-Game" You fix the two bakelite-plates and the Snowshoe-wipers in between tohether IN POSITION "First Player" - You always ONLY start a One-player-game.
Think of: Williams and Ballys have "Ball-Count-Unit BCU" and Player-Unit P-U". Lets say the pin is set for "3 balls per play".
The sequence of a 1-player-game is "P-U=1, BCU=1" -> "P-U=1, BCU=2" -> "P-U=1, BCU=3" -> Game-Over.
The Player-Unit ONLY steps forward in a multiplayer-game - example a two-player-game:
"P-U=1, BCU=1" -> "P-U=2, BCU=1" -> "P-U=1, BCU=2" -> "P-U=2, BCU=2" ... -> Game-Over.
So either a spare part or a spare unit or a "single-player-game".
In Switzerland / Germany its now 11:30 at night (23:30) - I go to sleep - I wonder what I read from You. Greetings Rolf