How do I crack substr hash?

[sprot]

no, i mean write your own program or script that will generate a collision. it doesn't have to be very fast or efficient because you are likely to find a collision in only 110,000 guesses when comparing only the first four bytes.

Do you know why the official version of hashcat does not support such type of hash? Is it possible to add this option? I wrote about this to author of this program, but doesn't received response. I have some source code to implement such option, but I was not satisfied with the speed. hashcat works very fast.
P.S. sorry for my English.