Thanks all - I do have aileron deflection ranges specified for both the certified and homebuild versions, they're identical (+20 to -15) but with marginal differences in tolerance. No rigging instructions were supplied, so thank you all for the tips.
The problem I have is limiting travel - my range is too great and there are no travel stops in the (aileron control system) design - either primary (at the bellcrank in the wing) or secondary (at the yoke). At this point I may have to engineer this; what I'd really like is to understand why this would be necessary, i.e. root cause.
Echo
Pilot DAR 's point about flap deflection - on this type, the UK (LAA) homebuilt specs have actually reduced flap deflection from 40 degrees (on the certified version) to 33 degrees (on the homebuilt) to prevent an observed unpleasant wing drop on stall at high AoAs.