10k/10k takes 45 days, 7 hours, 19 minutes.
I usually make more sp than 8k, bit less hc, but same sp/hc concept, believe based on build time it comes out to be: 1932 hc and 9126 spears.
The difference in strength between the three is decent, but not as big of a difference as the build time:
Nuke hitting 10k/10k:
Attacker Units: 0 0 6157 0 3374 0 213 0 0
Losses: 0 0 6157 0 3374 0 213 0 0
Defender Units: 10000 10000 0 0 0 0 0 0 0
Losses: 5836 5836 0 0 0 0 0 0 0
Damage by rams: The wall has been damaged and downgraded from level 20 to level 14
Time to rebuild lost D: 634 hours, 33 minutes
Nuke hitting 2k/8k:
Attacker Units: 0 0 6157 0 3374 0 213 0 0
Losses: 0 0 6157 0 3374 0 213 0 0
Defender Units: 8000 0 0 0 0 2000 0 0 0
Losses: 7011 0 0 0 0 1753 0 0 0
Damage by rams: The wall has been damaged and downgraded from level 20 to level 12
Time to rebuild lost D: 364 hours, 23 minutes
Nuke hitting modified 2k/8k D:
Attacker Units: 0 0 6157 0 3374 0 213 0 0
Losses: 0 0 6157 0 3374 0 213 0 0
Defender Units: 9126 0 0 0 0 1932 0 0 0
Losses: 7350 0 0 0 0 1556 0 0 0
Damage by rams: The wall has been damaged and downgraded from level 20 to level 12
Time to rebuild lost D: 323 hours, 28 minutes
Summary: 2k/8k takes 12% longer to rebuild than 1932/9126, whereas 10k/10k takes a whopping 96% longer to rebuild.