Beat eggs, salt, and vanilla in a large mixing bowl with an electric mixer on high speed about 4 minutes or until thick. Gradually add the 3/4 cup granulated sugar; beat on medium speed for 4 to 5 minutes or until light and fluffy. Add pancake mix; beat on low speed just until combined. Spread batter in a greased and floured 15x10x1-inch baking pan.
Bake in a 400 degree F oven for 8 to 10 minutes or until golden and cake springs back when lightly touched near center. Immediately loosen edges of cake from pan and turn cake out onto a towel sprinkled with powdered sugar. Roll up towel and cake into a spiral, starting from one of the short sides. Cool on a wire rack.
Meanwhile, add rum to peaches; set aside. Beat together whipping cream and the 1/2 cup granulated sugar until stiff peaks form. Unroll cake; remove towel. Drain peaches. Spread cake with half of the whipped cream; top with drained peaches. Spread with remaining whipped cream. Roll up cake. Place seam side down on a serving platter. If desired, sprinkle with powdered sugar. Cover and chill up to 2 hours. Transport in an insulated cooler with ice packs. To serve, cut into 1-inch-thick slices. Makes 10 servings.