I feel slightly guilty for setting off this discussion. I have ample critisism on Aster kits, but that is a slightly different matter.
It somehowseems to have eluded the readers, that my other Aster P8 thread actually is a very positive account on the performance characteristics of my completed Aster P8 kit.
With ample heat and steam generation, and a VERY smoth running machinery, setting off along the track at low pressure - without even the normal initial manual nudge - thus stunning the surprised driver (me)!

In my view, smoth machinery and enough power, facilitate extremely slow driving. My engine obviously has that. And I'm counting on changing the notion among Stockholm Livesteamers, that Asters are somewhat "finicky" to drive.
However, after building the Aster kit, I'm even more convinced, I would never quite trust a factory to build a smooth running engine. In general, I would expect a hobbyist taking his (unpayed) time to build, should make an exellent job of filing and fitting parts to assemble an engine. I would not be surprised if some factory assembled Asters aren't smoth running enough, to be able to crawl along the track - without load!
With Aster kits, this fitting of parts, seems extremely important (much, much more so than for a Regner kit). And this is my critisism; There seems to be no thought through philosophy of tollerances in design and manufacturing of Aster parts / engines. It is so blatandly ill thought through or tried out, that it takes a lot of knowledge and time to be able to assemble a kit correctly. It is true that one does not need a lathe or such to complete an Aster kit, wich makes for a very nice sort of kit. BUT - assembly requires one to be a seasoned mechanic, with experience and knowlidge. Or you might actually end up with an engine that almost wont run at all. A collegue of mine (a dentist by profession), has built 4 kits. The first 2 really don't run at all - because he trusted the parts coming from Aster to be correct, too much. (he also claims to have received a factory built engine for service, where inlet/ outlet of waterpipes for the axle pump, had been reversly mounted. He states "I'm not impressed by Aster factory assembly standards")
I am really stunned by the lack of thought through philosophy of tollerances in design and manufacturing of Aster parts and general layout, based on my experience with the P8 / BR38 kit. It really cannot be described, even mildly, as anything but poor engineering, but at times it amounts to downright faulty engineering. I myself, would not have accepted many aspects of the design. It's not about large changes, it's merely implementation.
Not that it's that important, but should it not be possible to cut down the number of types of screws etc employed in each design?!? Using M1,7 for fastening headlights is downright silly. 1) M1,7 is generally to be avoided, as a rare exceptional thread 2) there are no mechanical reasons for this extremely odd choice. (Considering that livesteam engines actually have a life expectancy of maybee 100 years(!), beeing passed on to future generations, this seems like a nice consideration; Don't make future spare parts an unnessessary difficult matter.
The lack of thought through philosophy of tollerances is even more surprising, since Aster themselves are going to assemble a lot of RTR engines. As for possible explanations, the P8 model is actually a few years old, I can't help wondering if Aster had not yet adopted 3D CAD drawing, but that doesn't explain everything. Lack of philosophy, and possibly not making 2 prototypes / zero series, are other likely causes. I know this very well, since I personally designed (and patented

, manufactured and assembled a mechanical vending machine in a small series of 300 machines last year. The design and manufacturing process would be basically identical.
Having said this, adapting and fitting Aster parts, you will get a wonderful engine, with it's specific Aster flair! Aster really tries to mimick the workings of the prototype to a degree, the other larger manufacturers don't, in my view.