For that Nov 2008 manual reinjection of cash, that was a month when no trade were being indicated by AIM, but where % cash had risen to north of 50%, considerably up from 33% desired average % cash. Fundamentally cash % spiked due to stock value declines, but not deeply down enough for AIM to indicate a buy action.
Others use the Vealie, where if a sell trade is being indicated by AIM and you consider % cash to be too high already you update things to increase PC without actually selling any shares (that would otherwise increase % cash holdings). Personally IMO that's a bit like selling at a relatively high price, as determined by AIM, and immediately buying the shares back again (at that relatively high price). I believe that my way of not using Vealies, but instead re-injecting at other times when AIM is otherwise quiet, is less prone to having in effect over-paid for the shares/stock.
Alternatively you could re-inject cash when AIM was signalling a buy trade, and scale up the amount of stock value AIM was indicating be purchased. But it may be a long time before AIM does indicate a buy trade, or as per my example AIM - no buy trades being indicated by AIM at all.
Looking at the charts for that AIM, it was clearly that November 2008 re-injection of cash that helped the AIM to relatively outperform overall, to produce a higher reward than had Vealies been used instead (or if cash were simply permitted to rise to relatively high levels).
Clive.
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