I swapped my 1 1/8" bore MC for a 1" when I converted to C5 Corvette front discs. The 1" bore MC is for a C3 disc/disc brake system and therefore does not have a residual pressure valve in the MC port for the rear drums (which I'm retaining). I want to add a 10# in-line residual pressure valve along the subframe under the driver's seat where I'd also replaced the OEM proportioning valve (the brass block) with an adjustable proportioning valve. My question is, does it matter whether I place the in-line residual pressure valve upstream or downstream of the proportioning valve? My OEM MC for disc/drum contains the residual pressure valve in the port for the rear drums suggesting an add-on in-line residual pressure valve should be placed upstream of the proportioning valve, but aren't you then "proportioning" that 10# of residual pressure to the rear drums suggesting it should be placed downstream of the proportioning so it holds the full 10#? Maybe I'm overthinking this, but any thoughts on this topic would be most appreciated.