With LD-AIM because of the leverage I increase BUY SAFE 5% with each consecutive BUY but I don't think it is needed with AIM - HI
settings of
0% Sell safe 10% BUY safe 10% MIN order size
should be OK. That would give a 30% hold zone which is still large for a bond fund but the idea is to keep collecting dividends, not trading a lot.
Instead of increasing SAFE by 5% on BUYS I would start with a little more cash than 20%. 20% would only allow 2 BUYS. 30% would probably be enough with a bond fund at this point, 40% if you want to be nervous.