Hi. I've done over 6000 miles on my Currie and I can tell you it's been an absolute trial of my backstreet mechanicing skills!
Firstly downhill performance. Set up correctly, next to zero drag. The adjustment and condition of the chain is important. The original chain is made of putty, contact your local Renolds chain supplier and get a good one, you may need to buy a 5 metre length (about £115 delivered) but that will last you forever! I've also turned up on my lathe a cylindrical tensioner from hard nylon to replace the original. Set the chain up with 8mm slack at the tightest point. DO NOT NEGLECT CHAIN TENSION! If you do the chain can centrifuge off the back sprocket and lock the back wheel at speed. That will cause an embarrassing underpant moment, it did me!
Next is binding brakes. Any contact between the rim and block is bad news, set them up with clearance at all points of rotation. If the wheel runs out of true it may be due to busted spokes, a common Currie fault. I ordered a set of custom 12g spokes from Central Wheel Components and after drilling out the rim and hub relaced the wheel at 2000 miles, I've not had to touch it since.
Tyre pressure are also crucial, my Currie is in a mountain bike that rivals the Titanic for weight, I run both ends at 70lb per inch. Fortunately I have a compressor which saves elbow grease with this.
Then all you will need to overcome is the unreliability of the motor (on my 3rd), and the fact it eats batteries every 1500 miles!
Good luck.