Here are some additional preliminary results from my root response
size research.  These results were from a zone signed with a 2048-bit
ZSK.

Note that different key rollover strategies were not researched here
(I have a separate set of results for that), so some DNSKEY responses
would truncate under some rollover scenarios at this ZSK size.

Referral sizes (Maximum truncation sizes):
range [629 - 845] min: NF/NS, max: AN/NS
[576 - 639] : 7
[640 - 703] : 98
[704 - 767] : 128
[768 - 831] : 45
[832 - 895] : 3

Referral sizes (Maximum overall sizes):
range [661 - 1185] min: NF/NS, max: AERO/NS
[640 - 703] : 16
[704 - 767] : 59
[768 - 831] : 55
[832 - 895] : 60
[896 - 959] : 26
[960 - 1023] : 42
[1024 - 1087] : 14
[1088 - 1151] : 6
[1152 - 1215] : 3

NXDOMAIN sizes (Maximum truncation sizes):
range [953 - 1298] min: @_/A, max: XN--HGBK6AJ7F53BBA_/A
[896 - 959] : 1
[1216 - 1279] : 270
[1280 - 1343] : 10

Other response sizes (Full response sizes):
range [410 - 2418] min: NF/ANY, max: @/ANY
[384 - 447] : 32
[448 - 511] : 112
[512 - 575] : 106
[576 - 639] : 122
[640 - 703] : 60
[704 - 767] : 82
[768 - 831] : 28
[832 - 895] : 15
[896 - 959] : 4
[1216 - 1279] : 282
[2048 - 2111] : 1
[2368 - 2431] : 1

Again, the two responses over 1500 are ./RRSIG and ./ANY:

2073	1669	254	@/RRSIG
2418	2014	254	@/ANY