I must say I am a bit lost .. but it seems 2 me u can somehow route the master out from desk 2 to the first 1.. there u can just use the optional out (assuming U have the ADAT card) and send that input to one of the of the ADAT buss out (1 to 8)... the same goes for anything on the inputs of the 1st desk...

All u need 2 do is connect the adat out from the first 01v to the adat in of the RME!

Hope this is what u r looking 4...
Let us know

PS - U might feel that it's more confortable 2 keep the adat outs in they're original 17-24 chs 'till u have everything in audio and the swap' em 2 the 1-8 for mixing etc...

Z