Nitrate dope will not shrink silkspan or silk. Nitrate dope is used to glue the covering to the wood, and to fill the pores of the fabric. Nitrate dope will not shrink the fabric, and it is not fuel proof. I suppose you could use Balsirite to stick silk on with an iron, but why would you do that and have the silk come off the next time it is in the hot sun? Butyrate dope is used after the nitrate dope to shrink the fabric and to provide a fuel proof finish.

If you use silkspan be prepared to recover and paint a year or so later.