I was playing with Optic raytracing app yesterday..
It looks like it may be possible to significantly correct the SA of the prime focus of C11 (when secondary is removed) with two lenses (RASA is achieving this with 4 lenses, last image attached).
The simulation was done at one wavelength only, so it is only to prove the concept.. obviously, single lenses should be replaced with CA corrected doublets (at least).
Also, as Stefan pointed out when I asked him a for opinion, the simulation is valid for optical axis only...
The whole thing was inspired by
this article and
this CN thread, discussing the issue.
The third image shows rays as they are without abovediscussed correction.