I have researched ‘elsewhere’ too and have nothing definitive. So far:

    1. The nee aluminium one ‘will be fine.’ What the suppliers mean when they say this is that it will be fine for THEM, not necessarily for us. I asked Keypart specifically and they didn’t know what I was talking about; they’re good, but understandably chiefly concerned with selling what they have to sell.

    2. Would VP market something that wasn’t suitable? Some suggest that the aluminium anode is actually a mix of various metals, including aluminium, and it ‘should’ be OK.

    3. I wonder to what extent VP are thinking of 20-year-old saildrives when they market anodes? We don’t all have new saildrives.  People like me cannot afford any possibility of an eaten-up saildrive.

    4. Some folk say that if you change away from zinc for one anode you should do the same for any others. I have a supplementary zinc pear anode for my MS25S and a Bruntons Varifold with zinc anodes (which dissolve in no time). Others say that because the prop & saildrive are electrically isolated it doesn’t matter if the saildrive is protected by an aluminium anode and the prop by zinc.

    5. Like you I didn’t buy an aluminium anode. I don’t know what to do, really. At the moment I feel that I will buy a pattern zinc one but I have always in the past valued the ‘reassurance’ of fitting one that costs a lot and comes in a nice blue box.