SF 750 foot rest triangle?

[lavfancier]

OK- heres another mystery (to me a least)

The rear footrest triangle on the SF3 has a pre-formed recess in the underside of the top tube - any ideas what the purpose of this is?

I've checked out other SF3  that do not have it but have seen it on late SF3 stamped GTL frames.
see below:
Cheers
LF

 

[sfcpiet]

As the bracket for a rear M/C is present, I'd say it was to create a bit of clearance for the RH brake linkage as fitted to US market bikes.  These had quite special footrests and gear/brake levers. 

piet

 

[lavfancier]

Thanks Piet- that would make sense.
LF