I've now got some A . square nylon aircrete anchors whose legs are supposed to spread out B. fischer GB8 plugs with helical fins C. normal screw-in frame fixings My aircrete blocks were the slightly stronger type than the solar blocks.
Results: A. In my blocks without a pilot hole you have to hammer these so hard I'm sure my wall would crack. I tried it on a lone block and 50mm from the edge the block cracked and edge fell away. If you put a pilot hole the fins do not spread and I could pull these out with a mole grip. They fixed in fairly strong but were in effect just a normal plug since if the pilot hole is all the way the fins do not spread. A pilot hole some of the way may be the best compromise.
B. Hammering in needs as much force as (A) but pull-out was very good.
C. Fairly far into the block (past half way) with 0.5mm smaller pilot hole than recommended, and tighten with screw. Pull-out seemed as good as with B.
Hum. So I'm not sure the special aircrete fixings are that wonderful. (C) is the best overall if your wall withstands the battering.
Anyone else got info to add ?
Simon.