Chime in I will. I don't have a Sun, but a Rans Stratus rather. My stratus is rated to 275 or 300 and I am 350. It's a great bike and carries me pretty well.
If the Sun EZ-1 is rated for 350, I would not be afraid of it taking 450. Don't sweat the frame! And other things like bottom brackets that clyde upright riders might be hard on, are not such a big deal on recumbents as we never stand on them. Get a good LBS to build that rear wheel!
As far as wheels go, I had a Sun Mammoth 36 Hole rim built up with DT Swiss spokes and I have their tension checked regularly. Unfortunately, that rim is is no longer being made. Wish I had bought 2 rims! My LBS suggested a Salsa Gordo (available in 40 and 48 hole models.) This will probably be my next rim unless I buy a trike. The rhynolite is a great wheel as well, but seems to top out at 36 Hole. Either are great wheels
2007 TerraTrike Cruiser (XL) Trike
2004 Rans Stratus XL LWB Recumbent
1999 Trek Navigator 200 21"
Last edited by tomdaniels; 06-13-08 at 09:00 AM.