Somewhere (TKD I suppose) it's written that the only suffixes following a verb used as an adjective can be the negation suffixes {-be', -Ha'} and the intensifier {-qu'}. I think it's logical that both can occur together. So I have no doubts that you can say {Duj tInqu'be'} with the intended meaning.

But other suffixes are excluded, do the answer to question 2 is no. It is easily understood, but ungrammatical.

TKD only describes using -qu' in this way. Further canonical examples have shown us -be' and -Ha'. None has ever shown us multiple suffixes, though I would have no problem accepting Duj tInqu'be' for not very big ship.

Although we have never seen any other verb suffixes, I would not at all be surprised to discover that type 6 verb suffixes are allowed, as in mayqel's *Duj tInba' obviously big ship or *Duj Dojbej certainly impressive ship or *Duj HoSghajchu' all-powerful ship or *Duj pujlaw' apparently weak ship. But until such time as Okrand does this, these suffixes are off-limits.

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SuStel
http://trimboli.name