Well if anyone else is in the same situation as I was I'll just add this:
I found that making the shrouds very short for extreme mast rake with my 70's step and base caused a problem due to the mast step link kit.
The base wouldn't go into the step correctly because of the pin. I don't know if this is common with the old steps and bases as I had to drill the holes for the link pin myself so might have done it slightly off, but I did follow the instructions.
After a lot of adjusting and measuring I discovered that to rake the mast with my set up, there is a rake limit where I can connect/remove the mast step link pin. So I swaged my shrouds so that they were in the highest hole on the stay adjusters at the point where it is just possible to engage/disengage the pin.
So you basically have to step the mast first, remove the pin, then adjust for rake by lengthening the forestay via the adjuster and putting the shrouds in the lower holes on the shroud adjusters. When you want to take down the mast you have to adjust back to the least rake again to get the pin in again, pretty annoying as this all takes more time.
Anyway I stepped the mast today at the newer rake setting (pin limit) and didn't bother adding more rake (can you blame me I wanted to get out on the water). I found the boat handled a lot better. I was doing faster reaches and lots of hull flying without worrying about the bows burying. I've still got a few inches between the blocks when sheeted in. I've got the original fiddle 4:1 blocks.
Just tiny adjustments fore and aft with my body weight made big changes in my boats pitch attitude. So I didn't find I needed more rake today.
By the way I don't know what the fuss is about tacking a uni-rig, I was only in irons once or twice today (15 knots) and got out very quickly all my other tacks were smooth and fast.