Anybody tried to mix these two sets? I'm thinking of keeping my MX20s up to 7 iron and adding the MP30 8,9,P. Problem is, there would be a 6 degree gap between 7 and 8 irons.

I would not mix the two sets as they are both very different clubs and it would be hard to have consistency.

Yep - different shafts, offsets, loft, swingweight.

What's wrong with the MX short irons Fraser?

Think its a good idea Fraser. You can specify the same shafts, lofts and swing weights. Sure Mizuno would do thsi for you. Offset help you get long irons in the air. I know a different make but Paul McGinley has TM RAC OS long irons and LT short irons. Same principle and works for him

I am currently testing LT's and 300 forged in the 8-pw. Its going fairly well mixed sets are the way forward as long as you get them spec'd out which can take some time. I also have stiff in the long irons and reg in the shorter irons. Its all good fun to play around!!!

good