Is your .024/.028 lash setting hot or cold? If cold, you are probably at .030/.034 hot. The optimal lash will be determined by varying the lash and making a test run to see what the engine wants. I generally loosen the lash no more than .004" and tighten the lash no more than .008". So the cold iron settings would be .020-.032 intake and .028-.036 exhaust. Aluminum heads would be around .014-.026 and .022-.030 cold. I've tightened the lash more than .008" but you start running into increase overlap and some poor low end running.
If the engine runs better with tighter lash, you might could use a bigger cam. If it runs better with looser lash the cam might be too big. Try the intake and exhaust separately to see if it wants more or less duration on the intake or exhaust. It could take a couple of days to sort out the valve lash.