I've taken the (relatively!) easy option, lowering the Bachmann Junior's saddle tank by 3mm and the footplate by 2mm, still allowing room for the Bachmann DCC chip.
Achieved by unclipping the cab and saddle tank, using a razor saw directly under the saddle tank, then using the razor saw to cut each base piece directly above the toolboxes, and re gluing
the base pieces with wheel splashers back in in position under the saddle tank. The smokebox saddle was lowered to accept the smokebox door and the front aperture was opened upwards to allow the smokebox door to sit 3mm above the footplate using a round grinding bit in a mini drill, and for it to be be glued in place.
The chassis end pieces that rest under the footplate were both lowered by 2mm using a diamond cutting disk in the mini drill, with the corresponding chassis securing lugs reduced accordingly, The front saddle tank securing plastic lugs were trimmed underneath to fit the new chassis position. If necessary 1mm can be taken off the top of the chassis weight and the top edges chamfered slightly.
I haven't altered the front cab windows, but they could be drilled out to a suitably larger size.
It makes for a much better looking loco, with the saddle tank 5mm lower than Bachmann's monstrosity! . Shame Bachmann didn't think to do likewise in the first place!