Welcome to the Starboard WS School forum and thanks for you kind comment!
I'm not sure a comprehensive "reference chart" exists that covers all conditions, board sizes, board widths, sail types and sizes, and sailor size/weight.
Pages 20 and 21 of the '07 Starboard catalogue will give you some good places to start.
Here's the link to the '07 catalogue.
It's huge (44.83 mb), but if you have a good internet connection, download it, and take a look at the "My Board" selection guides on pages 20 and 21.
Then take a look at some of the sailmakers web sites and get their recommendations for sail sizes and ranges for various wind speeds and I think you will have enough information to make some good choices.
Your 5.2 m2 rig is about as small as I would ever suggest for a GO 150/75 Kg. sailor.
When you have developed your skills to be hooked in, in the footstraps, and planing all the time, your 5.2 m2 rig will be good for around 22-27 knots of wind.
It would seem to me that what you need right now is a larger rig. so you can spend alot more time planing, hooked in and in the footstraps in lighter winds and flatter water conditions.
This will allow your skills to develop the most rapidly.
I'd think your next sail would want to be around 6.5-7.0 m2.
Then look for an even larger sail unless your winds are > 15 knots most of the time. Something around 8.5 m2.
Your GO 150 is a fairly wide board, and to get the most early planing performance from it you need a larger rig. This will be about 1 m2 larger than other sailors on smaller narrower boards.
Let me know if the suggested chart is helpful. If you need some links to sailmakers, let me know.
Hope this helps,