No the fitment of rpr (rudder pressure reducer),s actually is part of the fix to resolve the issue of crossover speeds. As i understand it below 1000ft agl only half the flow rate is available to the rudder (same psi) in the event of an engine failure full rate is restored, however the change over is seamless to the pilot thus very little info is published to crews.. .Regards the 800 series there is probably no published figures for crossover speeds as the min man speeds more than cover them. This assumption is made on historical grounds as there were never crossover speeds published for the classic series until the rudder issue arose and it was found that some min man speeds were below crossover speeds. Thus the 700/800 were certified with this knowledge so i think they left those speeds in the don,t need to know basket.. .Blip i,ve pondered the same question, but i can assure you from lot,s of work in the sim that it is definitly the case that more speed will keep you upright, maybe the aielerons and spoilers have a completely different effectiveness curve over the speed range than the rudder does ???