Scheibe TM 653-32 refers to conversion to C-model. It's only possible for
certain serial numbers and involves major work (changing the rear wing
attachments, engine mounts/engine), then standard C-model MTOW.

Scheibe TM 653-33 refers to conversion to D-model. For all serial numbers.
Major work, involving shortening of the wingspan, structural changes to the
fuselage, engine change and new prop, new fuel system, the MTOW 580 kg or
there abouts.

At 08:08 06 October 2020, Neal Stephenson wrote:
Good day,
Does anyone know what is required to upgrade a SF25B model to a C or D
model.
Basically the requirements to increase the all up weight (MAUW). to at
least the 610kg mark.
I see some of the later versions are up to 690kg.
(This will be in the experimental catergory)

Thanks in advance.
Neal
South Africa