Is there any rear caliper with e-brake & >38mm piston for 914/6GT ? Options

[amallagh]

My 914/6GT is struggling a bit with brakes having uprated to a 2.8 twin plug with about 280bhp.
It currently has S calipers up front and some 914/6GT rears with Porterfield R4 pads.
As well as heat the sticky track tyre set up could cope with more brake torque as well. (215/50r16 front and 245/45r16 rear). It is not a single use car - It is used on road as well as competitive rally and some trackdays.

There are plenty of 911 uprate options for the front, but without changing to a 911 emergency brake on the rear, then I haven't been able to find something to balance things at the rear. The current set up is properly balanced and there is no point in uprating the front unless I can uprate the rear. I really don't want to mess about with the rear arms by fitting the 911 e-brake system unless I really have to.
Is there any alternative rear caliper out there with a cable operated handbrake mechanism, with a >38mm piston like the original 914/6 calipers ? Anything from an Audi or VW for example that anyone knows will work in this application ?
Something with a 42 mm piston (like the Carrera rears) or even slightly larger would be ideal. Or has anyone fitted larger discs to achieve a similar upgrade ? If I could uprate the rears, then I could fit some Boxster front calipers on 280mm Carrera discs or a Boxster caliper kit with larger 300mm discs which will still fit under my 16" wheels which I definitely want to keep.

Am I wasting my time looking for an uprate option for the rears which still uses the 914/6 style cable operated handbrake in the calipers.

The crucial things is not having to change everything over to a 911 style e-brake set up. Any advice/options very welcome.
Regards
Andrew

[amallagh]

There are a lot of posts asking questions most of which I think I answered in my first post. But to add -
Porterfield Race pads and race fluid already in use. Car used extensively on road and track so a compromise is essential.
Brakes are overheating and fading at the front at full pace within a few laps. Would like a bit of extra break torque as well.
Extra power in the car simply means higher speeds and therefore more breaking.
I have discounted simply changing to Carrera front discs and it is not significant enough a step.
Thought is that Boxster calipers up front with larger pad area on Carrera discs will give extra brake torque and heat dissipation I need. But no point in doing that unless I can uprate the rears by a similar amount.
I would like a bolt on solution and would prefer not to have to change everything over to 911 e-brake which is a big job what with full strip, welding, refurb of old parts, painting, geometry, etc. I would wouldn't be doing the work myself and labour is expensive.
930 Turbo calipers and discs would be fine but too many £s

Hence my specific question about a possible rear caliper with 42/43/44mm posting and lever handbrake mechanism that could be adapted for use on the 914 trailing arms.

I see there are rear calipers around with this larger size pistons used by OEMs but question is has anyone made one work on the 914.

The idea is the larger piston in the 914/6gt caliper is another idea but is that possible (given all the e-brake adjuster complexity) and has it been proved by someone to be reliable. I'd only go down that route if there was a package of available parts that are proven to work (pistons, seals, adjustment compatibility). I've never seen this idea mentioned before so thinking the alternative rear caliper with larger piston is a more realistic option that someone might have tried ?