My trike is a Scorpion fs by HP Velotechnic, supplied by Kinetics of Glasgow. I ordered it online and specified a special traffic yellow colour (orange and black are standard), which I think is both highly visible and looks more delicate than the orange.
I decided "in for a penny, in for a pound"—well, lots of pounds—and therefore treated myself to the spec that I would want, rather than compromising and expensively upgrading step by step. HP Velotechnics offers a wide range of options, and the trikes are individually prepared at the factory in Germany, then checked and prepped by the dealer.
Seat: I decided to go for the carbon-fibre body-link seat, as it is lightweight and ergonomic. I chose to include "wings" which help keep one in the seat on corners, and of course the head-rest (wonderful to relax against when tired).
Gears: this was a simple decision for me as soon as I had read about the amazing 14-speed Rohloff Speedhub 500/14. I have always preferred sealed hub gears to exposed derailleur gears, and particularly with the tiny 20" wheels I feel that derailleur gears are very exposed on the trike, whereas the Rohloff offers evenly-spaced gears which can be selected at rest or under pressure and which are protected from the elements. Pricey but definitely the future. This also eliminates the ugly derrailleur extension tube on the boom, and altogether results in cleaner lines. The gear change is effected by twisting the right-hand steering grip back and forth.
Brakes: I opted for the best—individual hydraulic disk brakes from Magura Louise on the front wheels. These operate unhesitatingly in the wet and in the dry, the ventilated disks stay cool under braking and there is no risk of tyre damage from heated rims, and on such small wheels the risk of torsional stress in the wheel is minimal. I also chose a surprisingly useful feature new to me: an Avid V parking brake. This is a caliper brake on the rear wheel applied by a thumb-lever, and its application is obvious.
Lights: this is a touring trike first and foremost, so reliable lights are a must; I was more than relieved to discover that, compared to the dodgy cabling and flimsy lights and dynamos of twenty years ago, proper solutions are very accessible these days. I chose the Son hub dynamo (front right wheel) with halogen lighting, which not only comes on automatically but also stays on for a couple of minutes after the trike has come to a halt: an obvious safety benefit. The rear light was originally mounted on the seat-back, but I have moved it to the head-rest in order to fit the seat-bag; as a result the light is also a little higher. The hub dynamo causes minimal resistance, is always on, and never slips. The halogen light is brighter than my Land Rover's headlight...
Pedals: I chose Shimano pedals which offer clips on one side and normal flats on the other, so that I can cycle with ordinary shoes should I need to, although I usually use clips for security (heel strike can lead to horrible injury, don't even want to contemplate it).
Mudguards: I selected the full set, but disappointingly the front guards were both difficult to position (they would twist slightly and rub against a tyre) and would work loose, no matter how hard I tightened the fittings. I have taken the front guards off, which looks more aesthetic, and which means that if I cycle on wet roads my hands get a little spray on them (cycling through puddles on curves throws water over the cyclist, but this is surprisingly unimportant in practice). Presumably there is also slightly less wind resistance without the front guards—certainly it is a little quieter. The rear guard stays on and is indispensable, as otherwise I'd get thoroughly soaked on wet roads; it is also entirely reliable.
Suspension: the fs is fully suspended, making for an extremely comfortable ride, and I selected the gas-filled rear spring as it is fully adjustable. Having set it up it has proven trouble-free so far.
Mirror: I selected one, a Mirrycle, which is mounted on a small extension bar on the right-hand side of the handlebar. It is very useful, as turning to look behind is awkward at best on a recumbent, and I shall fit another on the left-hand side for added security.
Luggage: this is the weak point of the tadpole design: nowhere to attach bags! I do not want to add the weight of a carrier, although the Scorpion carrier is a very elegant one, suspended from the frame rather than pressing on the wheel-hub. Extensive searching on the internet led to Hostel Shoppe in the US, which carries an extensive range of well-thought-out recumbent accessories. From them I have Fastback pouches designed to hang beneath the boom and carry toolkit and the like. The main storage is the 11.5-litre Aeropod bag, suspended from the seat back, which was supplied by Angletech Cycles of Colorado Springs.
Power Idler: this gets quite techy... the immensely long chain passes underneath the seat, where the tensioned upper chain passes under an idler wheel. The idler can cause resistance if worn, and I elected to replace the original with a specially-engineered Terracycle power idler. No noticeable difference in resistance—the replaced wheel was still new—but hopefully this will last forever and be trouble-free.