I did 6 tests to see if items spawned closer to characters. All of them were done on Final Destination; 5 minutes; two Pikachu (hat and headband) sitting on each end; 3 stocks, 0% on both. Anything within the >> or << arrows on the stage counts for green/red. Anything outside them is neutral (anything borderline was considered neutral). Items set to medium. Current Evo ruleset items only (minus smashballs).
Of course, the neutral zone is a bit smaller than the red/green zones combined.
Test 1
Green - 3, 5, 10, 13, 14, 15, 16, 19, 20, 23, 26 - (11)
Red - 2, 6, 8, 18, 22, 25 - (6)
Neutral - 1, 4, 7, 9, 11, 12, 17, 21, 24 - (9)
G: 42%; R: 23%; N: 34% --- (65% to 34%)
Test 2
Green - 4, 5, 13, 23, 24, 26, 27 - (7)
Red - 1, 2, 3, 8, 9, 14, 16, 18, 22 - (9)
Neutral - 6, 7, 10, 11, 12, 15, 17, 19, 20, 21, 25, 28 - (12)
G: 25%; R: 32%; N: 42% --- (57% to 42%)
Test 3
Green - 10, 12, 15, 18, 20, 22, 24 - (7)
Red - 1, 2, 4, 5, 7, 8, 9, 11, 13, 14, 16, 25, 26, 27 - (14)
Neutral - 3, 6, 17, 19, 21, 23, 28 - (7)
G: 25%; R: 50%; N: 25% --- (75% to 25%)
Test 4
Green - 4, 5, 8, 9, 10, 12, 13, 14, 19, 22, 27 - (11)
Red - 2, 3, 11, 15, 17, 20, 21, 23, 24 - (9)
Neutral - 1, 6, 7, 16, 18, 25, 26 - (7)
G: 41%; R: 33%; N: 26% --- (74% to 26%)
Test 5
Green - 4, 5, 12, 19, 22, 23, 30 - (7)
Red - 2, 9, 10, 17, 20, 21, 24, 26, 28 - (9)
Neutral - 1, 3, 6, 7, 8, 11, 13, 18, 25, 27, 29 (11)
G: 26%; R: 33%; N: 41% --- (59% to 41%)
Test 6 was a little different. I put both Pikachus on the same side. Anything within the << arrows is R/G, anything else is neutral.
Test 6
Green/Red - 1, 3, 7, 10, 12, 13, 15, 16, 19, 26, 27 (11)
Neutral - 2, 3, 5, 6, 8, 9, 11, 14, 17, 18, 20, 21, 22, 23, 24, 25 (16)
G/R: 41%; N: 59%