In one of Crane Cams old catalog they recommend setting the lash .006 tighter with a iron block and aluminum heads and .012 tighter with aluminum block and aluminum heads.
I used those recommendation on a blown KB aluminum street Hemi block with a set of Dart water casting aluminum headson a motor I assembled and they prove to be dead on when I rechecked them hot on the dyno after running the motor long enough (20 to 30 minutes at or around 2500 RPM) to get the oil temp. up to 170F
I have seen those settings not work on a wedge motors with Eddy aluminum heads on a 400 iron block My old pump gas motor with those heads would vary right at .001 looser hot than cold(65 to 70 F shop temps. I would run the motor driving into town for 20+ minutes and the same amount of time coming back to the shop later and then check the lash hot on one side with the method of when exhaust opens, set the intake and then rotate the motor over clockwise until the intake opens all the way and starts to close a little past BTDC and then set the exhaust I would start the motor up after doing one side and let it run until I got at least 160+ F water temps agian on the temp guge and then do the other side.
In the morning with the motor cold and at or close to 60F in the shop the valves where tighter by .0005 to .0015

Cab, in a previous valve lash thread you recommended setting .002 looser when cold, with iron block and iron heads. Have you ever found that setting to be incorrect?

Looser lash is faster on everything I ever played with. I run the Valiant at .030

I has been a long time since I ran or raced a motor with iron heads, the .002 looser cold with iron heads and block is on that same chart recommending from Crane
The only time I used the stock recommended loose lash(.024 to .032) was on the old Isky and Mopar solid lifter cams and they always ran better with tighter lash, like .008 to .012 tighter hot
Try setting them at the recommended setting cold and then run it until warm(20 minutes +) and pull the easest valve cover and check two or three valves to see how they average, that way you know for sure what works on that motor for you

I set all my cast iron stuff .002 tight cold.

I have never seen valve lash close up on a warm engine, regardless of material.