[triumph1902]

As far as gun tips go...the thicker the liquid you spray the larger the tip you need. Base coat is a relatively thin so, usually, you would use a 1.3-1.4mm tip... with Clear coat, which tends to be less viscous, you want 1.6-1.7...primer tends to be even thicker so you can go 1.7-1.9 and then 1.9+ tips are for undercoats and spray glazes. I use a 1.5mm tip on My SATA because its big enough for clear and small enough for base as far a my gun goes. Also because I dont have a heated spray booth and spray in cool temps..I tend to reduce the clear more then usual so it lays flatter...of course this makes it more prone to runs.

You are absolutely correct that a 2 stage base coat /clear coat urethane finish would be the most durable, however it is extremely difficult to get good results with flat clear. I expect the SEM 1 stage urethane to last 3-5 years without fading as a daily driver, and during that time should it need repairs I can easily do them...and even if it fades i can just sand it and spray it again...the 2 stage will last 10 years but will be impossible to touch up and may not come out as well as the one stage...thats why I decided to stay with the one stage in this case.