drmini in aust wrote:
Mini K had 4 bags AYA4090, but I don't think the hydro bags
need to be a `matched set'- throughout the hydro era, various bag combinations were fitted to the Cooper S by the factory. They were not all front/rear = same.
I've run `71 GT front bags and `70 Minimatic rears for the last 15 years, it's not saggy one end or the other and the helper springs are originals.

I would say a fairly cautious yes, it could be done. I say up front, I have not done it.
The Hydrolastic Displacer Unit;-
By
gtmowog
Item 2 is a rubber spring and item 6 is the damper valve (shock absorber).
It is these two items which make for Soft, Normal, Stiff or Very Stiff Hyrodrolastic Suspension. The Rubber Springs so affect ride height, as does many other componets of this wonderous system.
So I would say, if I were to mix and match different rate Hydro Bags, then I would be putting stiffer ones in the front than in the rear, just as you have done.
If the were stiff ones in the rear and soft in the front, it could cause the rear to ride very high compared to the front.
This could be - could be - a cause of the problem that Lillee has with his Mini.
<EDIT> The Early RED displacers had a 'built in' spacer of 0.180", so again would be fairly important not to mix these with others. If you were to mix and match displacers, I would again suggest caution.