Having nailed my colours to the mast of P4 adherence, I'm all of a sudden not so sure! Let me explain...
I finally decided to tackle the conversion of one of my Bachmann 55xx's using the Ultrascale 'conversion pack' I purchased while ago. I assumed that the most difficult part of the job would be dismantling and reassembling the chassis and coupling rods etc. Fat chance!!
Having dismantled the chassis and removed the 00 wheels it became obvious that there are several major problems:
1) The significantly wider back-to-back gauge of the P4 wheels leaves a ridiculously large gap (over a scale foot!) between the backs of the wheels and the 'frames' (or chassis block in this case). Platsicard overlays are an option except you'd have to try to recreate the spring mouldings really.
2) The brakes don't line up with the P4 wheel treads - in fact they line up with - and actually touch - the flanges. The only option is to cut off the brakes and then try somehow to reattach them at a wider spacing - sounds like a delicate undertaking with potential for breakage! Oh yes, and you'd have to construct new brake rods.
3) The motion brackets foul the crank pins on the front wheels, even without the motion and rods attached. Not sure if there's a simple solution here.
In other words, while it may not be a particularly long list, they are serious enough issues to make me think it might not be worth the effort. In fact I'm tempted to think that no-one actually tried out this particular 'conversion' before releasing the conversion pack!
So my options seem to be:
1) Spend a good few hours hacking away at the Bachmann chassis in the hope that it might eventually look and work ok, but no guarantees.
2) Invest in a Perseverance etched chassis kit - more expense and still a lot of work but at least it can be built to P4 in the first place and would hopefully work. Although I'm not sure if the wheels in the conversion pack would be compatible as they have spacers to fit the 00 chassis.
3) Go back to 00 gauge! (Not difficult since I haven't really built anything in P4 yet bar a couple of experimental wagon chassis').
To be honest I'm tempted by option 3 - especially after seeing how good Chris Nevard's latest 00 layout 'Catcott Burtle' looks... I'm not sure I've got the patience and commitment to pursue this P4 lark!