[Coco] again 3.5" drive

[Diego Barizo]

Once I was sure that the 3.5" drive was working OK, I went fishing for a 
cable that would let me connect 1x 5.25 + 1x3.5 drives
Got one that is like this
3.5           5.25          3.5          5.25
(unused)    controller      drive        drive
||------------|||------------||----------|||
||------------|||------------||----------|||
||------------|||------------||----------|||

When I connect just one drive, the 3.5 acts as drive 1, and the 5.25 as 
drive 0
But when both are connected, and I try to access drive 0, both drives 
light up.
I removed the D0 jumper from the 5.25 (It had both D0 and D1, now just 
D1) and now both light up when accessing drive 1.
I'm guessing this has to do with jumper settings on the 3.5 drive 
(doesn't have real jumpers, but there are 4 holes in the circuit board 
in an area labeled DX, with pairs marked as 1 and 0, without any 
connection between them).
But if it were jumpered, wouldn't it always react as the selected drive? 
Or as drive 0 if working as single drive?
My final goal is to have the 3.5 as 0, and the 5.25 as 1...

Diego