<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">I do 1 set flat, then incline the bench to the first notch (~ 15-20 degrees), and do an incline BP. That's the same weight. Naturally, on my max flat bench, I can't do an incline BP.</div>
There's your answer. The flat bench in general allows you to use more weight. The difference in load between the two largely depends on the angle of the incline. If you use a slightly incline bench, your max weight should be fairly close to your flat bench max.
Hope this helps,
Dimitris