Seabreezer, from what I've seen of your wavesailing posts, I'd say you're underrating your abilities.

The 5'4" board you mention is going to be challenging for anyone learning. The thing that will make it a bit easier is the type of foil you stick under it. Any foil will act as an anchor to stabilise the board, but the longer the mast and the bigger the foil, (generally) the more stable it will make things. Long masts can be a little more challenging to learn with and have a higher chance of 'running aground'.
The stability of the board totally changes once the board is off the water surface. It's then all over to foil stability and that's where it gets trickier.
For anyone with talent like me I'd strongly advise against that board for learning. For you, it MIGHT work?? But it's a gamble. Have you tried any friends gear (of any size to get a reference point) to see what it's like? That would be a good starting point.
If you get it, seriously consider a wing down the track. They complement the board/foil really well for a range of light wind conditions.