Tom,
The reason I know that Crown likes the 4.52's better than the 4.54's is because of the extensive pellet testing I did right after I bought that rifle.
I shot 10 30-yd Challenge cards using pellets randomly chosen from three different tins of FX 13.4 gr pellets purchased from three different vendors (not on purpose - I was shopping around for the best deal). I weighed and measured the head of each pellet and put them in a 100 shot tray (numbered) so I could keep track of them. I then shot them with an SSL each at a single bull on the card, recording the velocity (kept the same tune). After shooting the whole card I would measure the POI of each shot and record. This gave me a ton of data to sort through and to simulate selecting only a certain head size or weight and see what my score would have been.
My conclusion was, for this rifle, there was a slight increase in the average score and a slightly smaller variation in score when I only selected the 4.52's (no matter the weight or velocity). I scored the target our usual way but also looked at vertical dispersion only (to try and eliminate wind as a variable). The 4.52's had a slightly smaller vertical dispersion also. To be honest, this didn't pass the statistical significance test at 95% confidence, but it was close.
This same thing did not happen in my other Crown with either .177 or .22 pellets. I found almost no difference (statistically not close at 95%) from sorting in any way. That was also true with my now long gone .177 Brocock Sniper and .22 and .25 FX King.
My current batch of FX 13.4 gr trash cans from Utah Airguns came with a sticker on the back saying it was 4.52. I have a Pellet Gager set (4.53, 4.52, and 4.51) that lets me check 48 pellets at a time. I use that to see if the first tin in the group gives me good results, then just pull randomly. For FT, I put then in a pellet tray I 3d printed with the skirts up so I can do a visual check to make sure none are badly damaged.
It is amazing what you can do with evenings when you don't watch TV and you are not grading homework, lab reports or tests!
Cheers,
Greg