Seems a bit outdated rule. First in the US it would be be a violation of the FARs to cloud fly, it would be very unwise and dangerious, every iPhone, iPad, android device has an app with a horizon, do not see those barred from the cockpit nor a way to enforce. As for me getting to a world gliding championship, not on a goal list of mine. My focus is on xc flying. Just thinking one of my favorite flights was also one of my shortest, flew 150 mile triangle using thermal lift while never getting more than 1,500 AGL. Winter flight in Southern Cal.

Most flights are not sancationed competitions, maybe more emphasis should be on having fun XC camps than competitions. Our sport needs more participants.

4.1.2.b Instruments that must be removed from the sailplane
The following instruments shall not be carried on board:
* Bohli, Schanz, KT1 or other gimballed compass
* Turn indicator
* Artificial Horizon
Software artificial horizons integrated with FR (fly compiuters) must indicate in their IGC files that AH function is disabled.

If you are a competitor, perhaps not the best choice (or if you were to rent to a competitor, or sell to one).