Roast the tenderloin, as directed. (usually 20 min per pound @ 375*), let it rest 10-15 minutes. Slice fairly thin, against the grain.
Split Hoagies and spread mayonnaise on the inside of both rolls. Put mustard on the inside of top roll.
Now assemble the swiss cheese on the bottom, then a layer of roasted pork, 3 slices of ham (folded to fit), 1 1/2 slices pickle, and then the top of hoagie.
Heat skillet to medium, or use a George Foreman (works very well). Spread outside of sandwich with butter or margarine, then grill until golden brown. If using a skillet, press sandwich with a spatula, then flip and press again.