In an older version of the OTRAG components, the different lengths of the tank modules were taken into account, but these result in only a limited number of useful parts for suborbital test vehicles. The current parts are limited to the representation of a useful and easy to create carrier rocket.
After a detailed study of the available documents I have created a version for KSP which is suitable for orbital flight and comprises 3 stages. The empty weights of the individual stages and engines was implemented on the basis of the scarcely available data. The thrust of the rocket engines was adjusted in accordance with the optimistic development targets, and is about 20% higher than the thrust values actually achieved. ISP corresponds to the actually measured and published values. Contrary to the original, the thrust remains constant during the firing phase, but you are free to override it yourself for more realism.
All components were developed exclusively for KSP standard. There are no ambitious adaptations for scaled variants of the KSP universe or "real solar system".
With the CSA OTRAG it is possible to transfer light satellites into a low orbit (75 - 120 km) (0.5t maximum), as long as these satellites brings approx. 250 m/s DV for circulation.
Contrary to the original, it is necessary in KSP to ignite the 2nd stage twice and to plan a free flight phase between the ignitions in order to achieve a to reach almost circular orbit.
In attempts to get along without overpowering KSP-SAS, I have the first and the third stage with RCS monoprop engines acting transversely to the direction of flight. The necessary tanks were accommodated with the payload on the third stage.