The following pictures show the LGB Rugens chassis mated with the Regner body of the Mh6 Engerth loco.
The tender articulation is a faithful reproduction of the real thing (In principle anyway).
The 0-8-0 LGB chassis is secured by two screws, the rear one is fixed through multiple plastic plates, all stuck together and stuck to the underside of the cab floor.
I did have to file away some of the external plating of the Regner lower bodywork to allow the driving wheels to have lateral movement to enable negotiation of an R1 point.
However, the loco will only negotiate one segment of R1, 2 segments together causes the loco to derail.
The articulation beam pivots about a central hex bolt as can be seen in the pics.
The decoder and speaker are fitted inside the tender which has plenty of room inside.
The last picture shows the maximum articulation of the tender.