Re: 8' mini mal travel bag
Wrap the board in something before you put it in the bag - bubble wrap (lighter but bulkier) or even felt carpet underlay (heavier but good level of protection) etc.
Keep in mind that it is the edges of the board that will generally be damaged - dropping a board flat probably wont cause too many problems, dropping on the edge will (and people will carry the board with an edge down). And as bags are thrown into the aircraft or cargo truck, its the nose or tail that is going to hit the wall.
Just stuffing the board bag with clothes or towels etc wont protect the edges that well. So it can be worth putting some extra effort there. Some people suggest using foam, like pipe lagging or some of those cheap swimming 'noodles', cut in half and taped to the rails. Even sticky taping some cardboard around the rails will help, or if you are using towels then do double or triple thickness around the rails and tape them in place. Extra protection for the nose and tail.
By the way, try to avoid putting the tape directly onto your board. It wont stick to the wax anyway and might be a pain to get the sticky stuff off where there isnt wax. I've seen people suggest wrapping the board in gladwrap (saran wrap) first, then place things around the rails then tape then on.
Make sure you remove your fins.
Once at your destination try to keep all the bubblewrap or foam etc rather than chuck it out, so you can reuse for the return trip.
Of course, to fit your board and all of the padding you will need a bag bigger than the board. 6inches longer is probably enough; plus you want to make sure the bag is several inches wider than your board - so dont forget the check the width of the bag against your board width.