I'm really interested in this upgrade. A replacement / retrofit two pot caliper that has an integrated parking brake would be a very clean solution. It would eliminate redundant costs of two sets of calipers (two pot upgrades plus a lightweight parking brake) plus two sets of pads plus any bespoke brackets required. All of those bits make it a fairly pricey upgrade, and simplifying it to a set of replacement calipers would bring the cost down and also keep weight off the car. Finding the replacement caliper with integrated parking brake might be easier said than done, though.
This is an upgrade that makes too much sense...reminds me of the rear oil cooler upgrade / OEM oil cooler delete that had far more benefits than downside.
LionZoo, we're both in SoCal. Feel free to contact me if you need any R&D resources either for desk research or car R&D. I have a Lotus friendly garage at home that is complete with all of the ramps, jack stands, jacks, tools & wrenches, vacuum brake bleeder, compressor, etc. for anything from R&D exploration to taking a Lotus apart and reassembling it.
So here's what I know from my investigation:
1) The HiSpec calipers use a standard spacing between the mounting bolts. The spacing seems to be shared among a bunch of other cars. I'll have my Lotus apart in the next week or so and I'll measure the spacing of our caliper to see if it's the same. If it is, adaptation might be relatively easy.
2) The HiSpec calipers use a pad that looks very similar to the Lotus front pad. It might even be identical. If the pads are the same and the spacing between the bolts and the top of the pad is similar to the Lotus calipers, that would mean it would almost be plug and play. Slight chance, but very intriguing.
3) If they're not plug and play, it might be best to run them with adapters in the same manner as the front AP adapters. Basically, put them towards the front of the car instead of towards the rear like the stock calipers.
4) Handbrake will require some adaptation, but doesn't look that bad.
5) HiSpec calipers don't have the best reputation. Apparently customer service is pretty non-existent if you have a problem (this seems to be a common thing with British suppliers, they're very nice to you until you need help). There have also been enough stories of HiSpec calipers flexing and failing that I was scared off.
Having said that, those calipers are cheap so it might be worth the investment just for a science experiment. Send me a PM and let's chat offline if you're interested. Or better yet, come to the next LCOSC board meeting on 1/13 at 11:30 am. Events ? Lotus Club of Southern California