@ipselute: The idea that i have implemented is that you create a new parameter for all STRUCTURAL rebar inside of your project files. This new parameter should be called "Multiplier". Both should be assigned to the REBAR category of elements. Then you simply edit your Bar bending schedules table to calculate the new number of total bars by multiplying the number of modeled bars by the multiplier parameter it now carries. Hey presto! you have just tricked revit into making it as though there were two layers of rebar i.e Top & bottom even though there is only one.
PS - Make sure your new multiplier parameter is classed as a 'Number'.
AND very important note !
This system will create an extra step in your workflow. As once this is set up correctly, NO REBAR weights and numbers will be correct unless you fill in this field at least with a "1" if it is blank it will incorrectly calculate your bar bending schedule.
Inevitably this will then create a problem with your TAGS and multi-Rebar tags. I dealt with this problem by creating 2 new different tags.
1 Tag which Has multiplier i.e:
<Multiplier>.<Quantity>.<Type>.<Spacing>.<Comments>
and one without i.e:
<Quantity>.<Type>.<Spacing>.<Comments>
Why?
When a rebar has a multiplier of more than 1 i use the first one above.
When rebar has multiplier of 1 i use the second one above or else you end up with a silly;
1x25.H16.200.Ubars
Totally unnecessary.
Once this is set up test it ofcourse that correct rebar weights are being calc'd.
My speed and efficiency in Detailing mundane massive slabs with 2 layers the same have increased several fold.
I hope this helps.
Good luck.