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The reducer will get you in the temperature range.
The CH255 is usually used for small repairs and will dry a little faster.
CH254 and CH253 are used for large areas and full paint jobs.
So the CH254 sounds good.
It’s not going to effect how the paint lays out.
Get the reducer and the temp in range, mix the correct ratios then spray a piece of scrap metal to be sure the surface temp is good inside you carport.
If it sprays well on your test panel, go to town. If it’s dry turn down the PSI if its orange peely turn up the PSI.