I have a 18.5 inch mav 88. I want to get a hogue forends. I know I need to get an action slide tube from a 500. But I don't know what to buy. I called Mossberg gave them my serial # the rep said I need a 6 3/4 tube. I measured my pump it's 7 3/4. Hogue forends are for 7 3/4 or you can use a 6 5/8 -3/4 but with a adapter nut. My question is can't I just buy a 7 3/4 tube and call it a day????? Please help!