Class 24 build... oh no not another Stoke engine.

Hi Toto.
Basically, all you would need to do is to connect the 'parallelled-up' pickups to the input of one decoder (as opposed to the two as shown in the drawing), then feed both motors from the output of the decoder, assuming that the current handling capacity of the decoder is adequate for the two motors total stall current. I built my Bulleid "Leader" with the wiring exactly as per the first drawing, as I use two decoders, both programmed exactly the same rather than separately and then setting the two motors up as a 'double-header'. Be aware though, that when connecting up the motors, you'll need to connect polarity opposite to one another, as the bogies are mechanically and electrically facing opposite to each other. Fail to do that, and you'll finish up with the bogies either trying to pull the loco apart or crushing inward towards each other.
Keith.
(Apologies for no drawing, but I don't have either a drawing program on my iMac, or the skills to use it if I did!)

 

Yes Toto, they were adequate for the job, and I've tried to standardise on them wherever possible, though even these are occasionally not physically small enough to fit into small loco's (the B4 springs to mind!)
Keith.

 

Yes Paul, they would both run in the same direction with both bogies facing the same direction, but when fitted to the loco, the bogies would be facing in opposite directions and would then be trying to pull the bogies apart or push against each other, hence the need to connect each motors connections opposite. When fitted to the loco, the foremost bogie would be pulling, rearmost bogie pushing so as to move the loco in the required direction. As you have the bogies more or less 'runnable', try connecting both motors to the same supply with bogies in the position they'd be in when fitted to the loco, as this may make what I mean clearer.
Keith.