Past participle of "spit" [closed]

My dictionary says:

past and past part. spit or spat

which I take to mean that either is acceptable. However, if I were writing about some spit which had already been spat, I'd use "spat" as the past participle to describe the spit:

spat spit

Using "spit" as the past participle in this case gives:

spit spit

which doesn't sound right.

In standard English, you generally have:

• come, plus its compounds (including become)
• run, plus its compounds
• bid (bid / bade / bid), but generally not its compounds (e.g. "forbid" gives "forbidden")

Depending on your dialect, you could have variations on this, e.g.:

• many speakers nowadays conjugate "run" as run / ran / ran, so e.g. would say "it hasn't ran"
• some speakers conjugate compounds of "bid" in the same way as "bid", so e.g. "they've forbid him from coming"; on the other hand, many speakers also use "-bid" as the preterite, e.g. "they forbid it" meaning "they forbade it"; I'm not sure what percentage end up with "-bid / -bade / -bid"
• as mentioned above, one or two other verbs, in particular inherently slang verbs such as "shit", are candidates for variation so it seems that some speakers may end up with this A / B / A pattern for other verbs.

There is:

Come -> came -> come
Outrun -> outran -> outrun
Overcome -> Overcame -> Overcome
Rerun -> reran -> rerun
Run -> Ran -> Run

It seems to work only for the two verbs "come" and "run", and their subsequent compound verbs. Perhaps someone else could come up with a unique example.