Ok - my thoughts for what they are worth.
I guess the most important thing you need to consider first is whether you want a shorter mal or a big shortboard type of board or some kind of hybrid. You should really consider getting a board that is similar in feel to what you normally ride so that you dont waste time and waves getting it wired when you hit some serious surf - or even worse get yourself hurt on a board thats so totally alien to you that you struggle to control it. Also get something that you will use back home - its always good to have a slightly smaller board than your mal as quick grab board that you can use in any conditions and is easier to handle and travel with than your longboard.
Personally I don't like the walden mid size boards although I am sure than many people love them. I reckon they are a bit heavy for their size and kinda boring to ride - which is only a personal feeling.
I would seriously consider a 7.3 7S superfish XL which is plenty of board for your weight and is an amazing travel board that will catch and comfortably surf everything from ankle to way over head waves with ease. The biggest and only real adjustment you will need to make is getting used to the speed dropping in and turning speed of the 7S over your longboard - it's quite a substantial difference. Beware though you will fall in love with this board - guaranteed.
If you look at a tuflite board you will be able to keep your size down a little due to the extra float of the boards and they are so damn rugged and light for travel, and there are dozens of shapes and styles to choose from. As much as it kills me to say this - the 8.0 Mctavish Carver in tuflite is a good option for a longboarder and it wont take you any time to adjust to the shorter length than your mal and it will probably paddle better than your fireball but be way faster on the wave and much easier to travel with. Its no secret that I reckon the carver is my least favourite Mctavish board but in tuflite they are pretty good boards.
Another really good option would be a Mccoy tuflite nugget - fun fun fun and fast and loose and a good range of sizes around the 8ft area. Mccoys are a real love or hate board but they are great paddlers, very easy to surf and very capable in all sizes of surf and in tuflite are tough as nails and also have excellent re-sale.
geez I could go on all night with this topic
If you ring a few shops you should have no problems getting a ride on a 7S superfish and also a host of tuflites. If you cant find any, give surftech a ring and ask who has demo boards in your area and I can get the contact details of your local GSI rep so you can ring him and get your hands on a superfish.
Bill