1968 Showman Reverb/1968 Bandmaster Reverb Cabinet Questions

[Toppscore]

I just purchased piggy-back clip-bars for my 1964 Bassman amp head.

I decided to check out my:
1) 1968 Fender Showman Reverb TFL5000D "taller" amp head
2) 1968 Fender Bassman Reverb TFL5005D "taller" amp head

Both 1968 taller Reverb amp heads only have two holes on the bottom panel.

ALL other 1960s "short" Fender amp heads have four holes for the four clip-bar screws/bolts/nuts, etc.

I cannot locate pictures of 1968 taller amp heads (Showman Reverb & Bandmaster Reverb) with installed piggy-back clip-bars. Has ANYONE seen The Showman Reverb or the Bandmaster Reverb with piggyback clip-bars factory installed?

I have seen several photos of the taller 1968 Reverb amp heads with two knurled thumb-screws and bushings installed in the Reverb amp's inside two bottom panel holes. Yet there are not four holes for the clip-bars.

I have mostly seen 1968 Fender Reverb amp heads with nothing in those two holes.

I have seen many "black bagged reverb tank units" installed on the bottom panel instead of the back baffle board.

My questions are:
1) Did the taller 1968 Showman/Bandmaster Reverb amp heads ship with clip-bars from the Fender Factory?

2) Did the taller 1968 Showman/Bandmaster Reverb amp heads ship with two (2) empty holes that were pre-drilled? Maybe Fender decided the taller reverb amps were too tall and too heavy to be used with speaker cabinets tilted back?

3) If all of the "shorter" 1960s Blonde Brownface Blackface & Silverface "short" amp heads shipped with four (4) holes in the bottom cabinet panel for the four screws/bolts to manage the clip-bars, why are there only two (2) holes in the 1968 taller Reverb amp heads?

4) If Fender shipped the taller 1968 Fender Reverb amp heads with two (2) chrome knurled knobs and their bushings installed in those two holes, what are the knurled knobs actually used for?