A true sailing Jedi would tell you that a spinnaker is NOT an upwind sail, no matter what the wind speed! Rather than wasting energy trying to figure out how to use the sail in a way it was never designed to be used, you would be better off figuring out how to get your boat going in light wind using the correct sails for that point of sail. Everyone else uses their Genoa for upwind work, and so should you!
Having said that, if one DID have an extremely flat asymmetric that could be used effectively for upwind work, tacking would present a problem. Outside tacks would be extremely difficult since you are trying to haul the clew of the sail forward directly into the wind, so the body of the sail will become a giant air brake as it fills. The most likely result will be that the sail will end up nicely wrapped around the forestay. If you had it on a furler it would be a simple matter of furling it, tacking, and then unfurling on the new tack. Obviously you don't have that option, so perhaps your best bet would be to tack it like a Genoa; through the fore triangle. You may need to drop the Halyard down a bit to allow the head to pass inside the forestay. Maybe even fly the sail from a genny Hayward if you have a spare. Obviously this would only work if you have a masthead rig, or a fractional spin halyard on a frac rig.
Again, I doubt very much that using your asym in this way will meet with very much success, aside from providing all kinds of entertainment for your competitors!
If you really want to get your boat going in light wind, start a thread on that subject, and we would be quite happy to help you sort it out young padwan!