Originally Posted by: Simon KeyesWhat I'm asking is the transitions appear difficult initially ; I assume with continued practice that this become achievable and almost a natural action ?[/quote]

Reiterating for clarity, the short answer is yes. Stated in the last sentence of paragraph three and expanded upon in four of my previous post.

From your mention of "power chords in the bank" I thought you must have started F2. I don't recall them being taught earlier here, but it's been a while. Unless you were mistakenly referring to the "5-CHORD POWER-PACK" (colloquial GT jargon) lesson in F1 which in retrospect I now think you were, something entirely different from power chords per se, as you'll discover when you start F2.

[quote=Simon Keyes]One thing that seems very important seems to be thumb position.........????

Thumb position is definitely important but placement taught is a guide. Guitar necks and individual hands and fingers are different. Like strumming or how to hold the pick, don't over think it or get too rigid about it, figuratively or literally.

Discomfort stretching for reach is normal when starting, but as time goes by and your muscles adapt you'll realise what is a reasonable stretch and thumb placement for your hand posture to stand clear around the neck and fingers and tips to present for clean chords for you and what isn't, or is working right and isn't. As long as the thumb is more vertical than horizontal for most (open) chords and supports the fingers with the necesssary leverage.

For instance I defy anyone to play open F with their thumb vertical unless they have hands like Godzilla, but by the same token don't get into the easy trap but bad habit of laying the thumb horizontally along the neck for that chord either. Adaptive awareness is key.