Firko from memory those mitas trial are a bit like the thick chocolate block pattern on the old bristone / dunlops, not sure which it is but you know the type with the solid blocks.
Tyre worked fine from what i remeber but the tread wasnt chewing gum like the X11, but then being stiffer it did spin up easier so it was still good for most DT i road on and i road some road base goat tracks ( never got a flat either ) i think with all these trails type tyres its like the speedway tyres too. Fo what ever reason the speedway dont wokr on the DT that well, its either in the wall or the size and flex in the knob. Even with the sipes inthe Speedway tyre it wants to run upright for drive rather than side on. On my modern MX a speedy just likes to fish tail back and forth.
I cant see any reason that you couldnt even ride on a road tyre on the rear of a old DT, there might be better tyres out there, but at the end of the day it goes around and around. i have a few old had 19" speedways here for free if anyone wants em, pay your postage. cheap way of getting your modern on the track for prac day without having to change the rear rim to a 18", but look out !