Thanks for the info.

I'm not very familair with the scrypt code but I took a look. Based on the name of the function
"scrypt_1024_1_1_256" I assume those are the parameters N, r, p & hashsize. 1024 is the default
N but can be changed from the command line. I found no mention of r or p paramenetrs in the code
so I assume they are hardcoded at 1, as implied by the naming of the function..

This would suggest that "-a scrypt:8192" won't work for scrypt8k. Have you tried?