Fitting zone valve query

[Daaave]

Hi all, I have a 28mm zone valve for a C Plan I want to fit and would appreciate some advice please.

I’m looking for the best way to adjust the existing pipework - my idea is to fit the valve at the green circle, tee off beneath it for the vent pipe and cap off the reducer at the cylinder (red)

Any reasons why this wouldn’t work? I guess I’m concerned about the vent pipe being the path of least resistance for HW if it’s that low, but I figured it would have to be before the zone valve in any case

Thanks

 

[Madrab]

I presume the current pipe out of the top of the coil is the return/vent? Ideally, in that scenario, you'd want the vent at the highest point to avoid airlocking the coil
Not sure why you want to go to a C plan though? Surely converting to an S/Y system would be much more efficient?