With PSLV you can buy the physical silver for 27 $USWith my purchase of today I have over 10,000 oz of Ag and I am eligible for the physical redemption (10 London Good Delivery Bars). (ie: You need at least 27,686 shares of PSLV shares for 10K Ag).
The future physical redemption of investor with 10K oz of Ag will reduce the number of units and will increase the short ratio.
If you put a sell of your PSLV shares at a high price, the shorters will not be able to borrow them.
Since the short ratio of PSLV is over 50%, these shorters will soon be cook.