The Monolog is slightly larger than the Osiris and Wind 50. Not by much, but more volume. I have flown it on both 5S and 6S. I definitely preferred the 6S setup. It is a much more efficient setup. I agree with Dana that 5S is more convenient if you are going to be jumping in to a 10s full blown 2m soon, but if not, then I would definitely go 6S. It is much easier on the equipment as the amp draw is lower and things run cooler. Even if you think a year or two down the road you might go 2m, then go with 6S. By that time, you'd need new packs anyway.

F3A Unlimited isn't like a lot of the larger online stores. If they have a sale, it is because they are overstocked or just offering good deals. It truly is 30% off as it wasn't that long ago that it was more expensive. I would call them and see how their stock looks. Anna is great to deal with and if they have a bunch in stock, it may last a while, if not, you might want to jump quickly.

Arch