Khasiana does get to a reasonable size, but it's just short of bulletproof.
Ventricosa is next on the bulletproofness list
these are the MOST TOLERANT.
Others compatable with windowsills are: alata, sanguinea, maxima, burbidgeae, fusca, x Ventrata, x Emmarene, macfarlanei, and ephippiata. All of these are ones that i have grown on my windowsill successfully, except emmarene and khasiana. Both of those are VERY tolerant though.