Very unlikely. The important thing to consider is the hight between the top of the forestay (where the halyard goes) and the normal position for the end of the pinnaker pole. Given the difference in size between 19 and 30 ft boats it is unlikely that the dimension for the 2 boats will be in the same ballpark. What are the rough dimensions for boat boats and what is the lenght of the spinnaker from head to foot?
Also, are they both masthead rigged? It just might be possible to fly one from a mastead rigged 19ft on a fractional rigged 30, although I suspect the area would still be very small.