No, suspension is not possible
I once put a LT Manitou (100mm) on a non corrected Miyata and I ended up with a bike that doesn't excel on singletrack and looks a bit weird. Nevertheless it still does a good job on other tracks, but I would get rid of the fork if that particular Miyata was my only bike.
If you go for a fork with max 50mm, consider: What decent fork do you know? I have a RondWP HydroPro2, what I consider one of the nicest with about 50mm travel, but I would be equally happy with a rigid fork.
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