I'll be stiffering you'll be stiffering he'll be stiffering we'll be stiffering you'll be stiffering they'll be stiffering
Future perfect
I'll have stiffered you'll have stiffered he'll have stiffered we'll have stiffered you'll have stiffered they'll have stiffered
Future perfect continuous
I'll have been stiffering you'll have been stiffering he'll have been stiffering we'll have been stiffering you'll have been stiffering they'll have been stiffering
I'd be stiffering you'd be stiffering he'd be stiffering we'd be stiffering you'd be stiffering they'd be stiffering
Past
I'd have stiffered you'd have stiffered he'd have stiffered we'd have stiffered you'd have stiffered they'd have stiffered
Past continuous
I'd have been stiffering you'd have been stiffering he'd have been stiffering we'd have been stiffering you'd have been stiffering they'd have been stiffering