Warning, this verb may not exist. Conjugation is given as example.
Affirmation
Simple form
I should stiffer you should stiffer he should stiffer we should stiffer you should stiffer they should stiffer
V-ing form
I should be stiffering you should be stiffering he should be stiffering we should be stiffering you should be stiffering they should be stiffering
Perfect
I should have stiffered you should have stiffered he should have stiffered we should have stiffered you should have stiffered they should have stiffered
V-ing perfect
I should have been stiffering you should have been stiffering he should have been stiffering we should have been stiffering you should have been stiffering they should have been stiffering
Negation
Simple form
I should not stiffer you should not stiffer he should not stiffer we should not stiffer you should not stiffer they should not stiffer
V-ing form
I should not be stiffering you should not be stiffering he should not be stiffering we should not be stiffering you should not be stiffering they should not be stiffering
Perfect
I should not have stiffered you should not have stiffered he should not have stiffered we should not have stiffered you should not have stiffered they should not have stiffered
V-ing perfect
I should not have been stiffering you should not have been stiffering he should not have been stiffering we should not have been stiffering you should not have been stiffering they should not have been stiffering
Interrogative form
Simple form
should I stiffer? should you stiffer? should he stiffer? should we stiffer? should you stiffer? should they stiffer?
V-ing form
should I be stiffering? should you be stiffering? should he be stiffering? should we be stiffering? should you be stiffering? should they be stiffering?
Perfect
should I have stiffered? should you have stiffered? should he have stiffered? should we have stiffered? should you have stiffered? should they have stiffered?
V-ing perfect
should I have been stiffering? should you have been stiffering? should he have been stiffering? should we have been stiffering? should you have been stiffering? should they have been stiffering?
Interro-negative form
Simple form
should I not stiffer? should you not stiffer? should he not stiffer? should we not stiffer? should you not stiffer? should they not stiffer?
V-ing form
should I not be stiffering? should you not be stiffering? should he not be stiffering? should we not be stiffering? should you not be stiffering? should they not be stiffering?
Perfect
should I not have stiffered? should you not have stiffered? should he not have stiffered? should we not have stiffered? should you not have stiffered? should they not have stiffered?
V-ing perfect
should I not have been stiffering? should you not have been stiffering? should he not have been stiffering? should we not have been stiffering? should you not have been stiffering? should they not have been stiffering?