excelsior 3rd down tube

[29 excelsior]

I have been trying too get info on 3rd down tube,added extra single down tube added to 1929/30 duplex framed excelsior"s.
see attached photos.no doubt added after leaving works,these mods were done to stop front end flex frame twisting,.
I am considering adding 3rd tube too my 29 500cc excelsior,with intention's of racing in hill climbs etc.phil irvings early motorcycle books refer too frame strengthening along these lines.should I muck with original frame?(needs retubing)
Controversial idea?

my thoughts are motorcycles history starts after it is delivered,all things done after factory are part of bikes history,

not many bikes spend their life as delivered,repairs and mods done over its life are its history and should be left as is.
as my bike isn't original, with non matching eng box and frame basket case I would like to improve with what was likely to happen if bike was raced or took part in reliability trial etc..as both attached bike have.no they aren't my bikes
cheers tony
will try too attach in next post

[DAM]

Like this one ?

It's the only one I have seen with the extra tube.

[29 excelsior]

Yes DAM like the bike pictured .having trouble down loading photos
cheers tony