So the maximum number is fixed at 9 in v10.5 and not related to anything else? (I have V11 and it just doesn't work for the type of work we are doing. V12 has the same issues). If there is an increase in allowable External Lookups inf V11 I might re-install it for this project. Otherwise I'll follow your advise. Tedious, but at least doable.
As always, thanks for the expert help.