mat_phong 0 // Disable phong for flatter shading
mat_disable_lightwarp 1 // Disable light warps
mat_reducefillrate 1 // Simplify material shading and use some DX8 features
mat_hdr_level 0 // LDR
r_cheapwaterstart 0 // The distance at which transitionary cheap water starts. Has less reflectivity.
r_cheapwaterend 400 // The distance at which fully cheap water starts. Does not reflect or refract and it is solid
mat_bumpmap 0 // Disable bumpmap materials
mat_specular 0 // Disable specular materials
r_shadowrendertotexture 0 // Do not use two materials for shadows

It's not quite dxlevel 81, but it's sorta close:

[code]
mat_phong 0 // Disable phong for flatter shading
mat_disable_lightwarp 1 // Disable light warps
mat_reducefillrate 1 // Simplify material shading and use some DX8 features
mat_hdr_level 0 // LDR
r_cheapwaterstart 0 // The distance at which transitionary cheap water starts. Has less reflectivity.
r_cheapwaterend 400 // The distance at which fully cheap water starts. Does not reflect or refract and it is solid
mat_bumpmap 0 // Disable bumpmap materials
mat_specular 0 // Disable specular materials
r_shadowrendertotexture 0 // Do not use two materials for shadows
[/code]

also, you can add this [url=https://raw.githubusercontent.com/mastercoms/mastercomfig/release/mastercomfig/dxsupport_override.cfg]dxsupport_override.cfg[/url] into your custom folder to set a few commands you can't set manually.

thank you very much