Got a few questions regarding inflatables and downwinding.

Bit of background, been supping for years on allround style boards; a couple of years ago got myself and the Mrs a pair of Starboard Drives (her first board) with the intention of surfing mine and paddling on the river with her, and possibly getting her to catch a few small waves. Well, we've had a lot of nice paddles in the river and I've done plenty of surfing but the wife is too scared of the waves to try, even in knee high stuff. I've since sold my Drive and got a Converse so it will fit on a plane. Lots of fun on a wave but not as much now for flat water paddling, especially if there is a head wind. So that leads to the topic, thinking of selling the other Drive and getting a pair of inflatables.

From other threads I've read 14" or longer is the go for downwinding (which I'm keen to have a go at), but are inflatables any good for it? The new breed seem pretty stiff if pumped up properly. The other thing is if the wind is over 15 knots I'll be out windsurfing, definitely if it's over 20 knots. Is it even worth trying to catch runners in 10-15 knots? If the answers are no I may as well get a pair of 12'6" so they're lighter to lug around on holiday.