Do you only have one
jib halyard ? If you have two
jib halyards then use one of those for your topping lift, that is quite common. If you only have one there is going to be another sheeve for a second so maybe you should add one instead of the topper.
That way you have a spare jib of spin halyard if needed.
Now that I think about it perhaps your boat did not have factory spin gear so you are using the second jib halyard for the spin. In that case I think the spin halyard is run to a seperate block at the mast head on a bit of an extension. You may have to go that route.
Gary