Not when you are sailing according to F16 rules, these forbid the use of a jib when sailing 1-up.

In general however (other classes etc) 1-up only refers to singlehanding a boat; it doesn't say anything about the rig used. But the F16 rules do something about the rig that can be used.

When I'm using the identifier 1-up on the F16 forums then I'm actually refering to the F16 definition of 1-up and that is without a jib

Hope this clarifies things