For those who didn't find the thread, there is another discussion about rear caliper options here:
Starting with post #80, it includes an interesting discussion about alternative two-pot brake calipers from AP (p.s. ignore the discussion about alternative mechanical parking brakes -- it didn't go anywhere). Specifically, AP (who manufactures the "Lotus two-pots") makes two other calipers, the CP5317 and CP5316, that have identical mounting and brake pad dimensions to the Lotus two-pots, but come with smaller pistons than the 44mm Lotus calipers (41.3mm for the CP5317 and 38.1mm for the CP5316). This gives you a range of possible "native" brake biases when combined with the stock Lotus two-pots (or each other).
Based on studying this information and the spec sheets from the AP Racing website, I purchased a set of CP5317's from a shop in the UK. I went with the 41.3mm because I use wider rear tires, I figured I could always soften the rear brakes with softer pads, and frankly, they were cheaper than the CP5316's (I can only guess why).
The good news: Using aftermarket two-pot mounts (which are available from several suppliers here and across the pond), they bolt right in, and use the exact same pads as the two-pot fronts, so it makes it easier to carry extra/different pads to the track, as they are all the same. And there is a definite improvement in braking, as the rears are doing a lot more work now.
news: If you really had to be ham-fisted on the brakes to trail brake before, you don't anymore
. I ran them at Laguna Seca in July using Carbotech XP10's front and rear, and was almost caught out a couple of times by how much
rotation I got in trail braking (once at the top of the Corkscrew). I need some more time running the car on flatter tracks to see if I should tweak the brake bias forward a bit (with less grabby rear pads). It forces you to be more subtle/precise on the brake pedal while rotating the car, but it the long run, it very well may be faster.
The bad news: Although I purchased them at a discount as part of a winter promotion, it took over 5 months
to get these. Apparently AP was completely out of stock, and felt that there was insufficient demand to put the next run anywhere near the front of the queue. A lot of grumpy/sad/apologetic emails between me and the retailer (although it basically was out of their hands).
BTW/FYI: What the posts don't mention is that the CP5317 and CP5316 have bleeder screws at the top of each piston (which is good), but that puts the input port on the face of the inside cylinder. When mounted using an adapter bracket on the leading side of the rear hub, the input port is facing directly at the rear shock, so the regular-style Elise/Exige brake hoses will not work. This setup requires a banjo-bolt type attachment to the caliper; the good news is this is essentially the same kind of hose shops sell to put 4-pots on the front, so they are available from a couple of sources off the shelf.