I wouldn't say that there are any hard and fast rules regarding CG location.
For a conventional airplane to be positive stable in pitch, its CG most be ahead of the airplane's Neutral Point NP.
The distance between CG and NP is called static margin and is expressed as percentage of the main wing's MAC.
The static margin may be between 5% and 15% of the MAC, so there's plenty of room to play here (no hard rules).
When the static margin is zero (CG coincident with NP) the aircraft is considered
"neutrally stable".
Which means that the spot you choose for your CG within the stable range is to some extent up to your personal preference - how you want your plane to handle.

Low wingloading gives you low stall speed, but it doesn't make your plane positive stable if its CG is located aft the NP, this is a rule that applies to any airplane that's heavier than the air, including your light wingloading foamies.
Since they have low wingloading, they can fly slower without stalling, which gives you more time to react and make corrections.
Anyhow it would be much interesting to know how close your foamie's CG actually is to its NP.