Bootable PCjr cart layout:

                                 
ScubaVenture:                     Byte Offset in .IMG 
Side 1, track 0, Sectors 1-9 +    [1200]
Side 0, track 1, Sectors 1-9      

Mouser:
Side 1, track 1, Sectors 1-9 +    [3600]
Side 0, track 2, sectors 1-9      

River Raid:
Side 1, track 2, sectors 1-9 +	  [5A00]
Side 0, track 3, sectors 1-9 +	  
Side 1, track 3, sectors 1-9 +	  
Side 0, track 4, sectors 1-9

Pitfall II:
Side 1, track 4, Sectors 1-9 +    [a200]
Side 0, track 5, Sectors 1-9 +
Side 1, track 5, Sectors 1-9 +
Side 0, track 6, Sector 1-5  

Demon Attack:
Side 1, track 6, Sectors 1-9 +    [ea00]
Side 0, track 7, Sectors 1-9 +
Side 1, track 7, Sectors 1-9 +
Side 0, track 8, Sectors 1-9 +
Side 1, track 8, Sectors 1-9 +
Side 0, track 9, Sectors 1-9 +
Side 1, track 9, Sectors 1-9 +
Side 0, track 10, Sectors 1-9 +
Side 1, track 10, Sectors 1-9 +
side 0, track 11, sectors 1-9

Microsurgeon
Side 1, track 11, sectors 1-9 +	  [19e00]
Side 0, track 12, Sectors 1-9 +
Side 1, track 12, Sectors 1-9 +
Side 0, track 13, Sectors 1-9 +
Side 1, track 13, Sectors 1-9 +
Side 0, track 14, Sectors 1-9 +
Side 1, track 14, Sectors 1-9 +
Side 0, track 15, Sectors 1-9 +
Side 1, track 15, Sectors 1-9 +
side 0, track 16, sectors 1-9

Crossfire
Side 1, track 16, sectors 1-9 +	 [25200]
Side 0, track 17, Sectors 1-9 

Mine Shaft
Side 1, track 17, sectors 1-9 +	 [27600]
Side 0, track 18, Sectors 1-9 

PCjr colorpaint
side 1  track 18  sectors 1-9+   [29A00]
side 0, track 19, sectors 1-9
side 1, track 19, sectors 1-9
side 0, track 20, sectors 1-9
side 1, track 20, sectors 1-9
side 0, track 21, sectors 1-9
side 1, track 21, sectors 1-9
side 0, track 22, sectors 1-9
side 1, track 23, sectors 1-9
side 0, track 23, sectors 1-9
side 1, track 24, sectors 1-9
side 0, track 24, sectors 1-9
side 1, track 25, sectors 1-9

All ROM images load to 2000:0 and then jmp (retf actually) to 2000:3.
There were minor fixups required to most of the carts to bypass copy
protection and properly re-vector interrupts from any hardcoded segments to
the segment the boot disk uses.  Sadly I don't have notes of what needed to be fixed
for most of the games (I started this project years ago), but it shouldn't be
too hard to rip the binary data off this floppy and compare it to the original .jrc
files used.
 


Pitfall 2:
It revectored a hardcoded address for int 09 to D800:a5f3.
Since we're booting at 2000:x, it had to be changed to 1800:a5f3
Another int was also hard coded to E000:x  since we're booting at 2000, I just
changed it to use CS, like it should have been in the first place. 
Later, it attempts to overwrite CS:0 (the 55 in the rom signature of 55aa)
and then checks it later.  If it were running off ROM, this would be harmless.
I changed it to write 55 instead of 0.



Microsurgeon only required 1 fixup:
E000:0000674E  mov  byte cs:[6762],9C 
This line overwrites data in its own vector.
If running in ROM it won't get clobbered, but running in RAM it will crash.


Crossfire needed a tiny fixup at the start because it used the default cart load vector at 0:60.  
I just patched it to retf to the start of the cart independent of the segment.


Colorpaint seems to be broken on a true PCjr but does work in PCjr mode in dosbox.  Grr.