Hi Clive, I'd go along with 50:50 allocation to start as long as the 50% is not in true cash. The 50% should be in a mix of cash and bond or high yield stock funds such as PFF.
The would make AIM compatible with Buy and Hold assett allocation portfolio, with AIM taking place of rebalancing.
Personally I use 60% stock and 40% bond/cash. I think for diversified index ETFs it's enough on the cash side.