Time to replace the office 2951s with 4351s.  Since the Internet pipes are 300 Mbps, we purchased the FL-44-PERF-K9 upgrades, which bump the throughput from a 200 Mbps to 400 Mbps cap.  I entered the PAK on the Cisco License Portal, installed the license, but noticed upon testing there was still a 200 Mbps limit.  The license commands indicated that the license had been installed, but not enabled/activated.

Router#show license feature 
Feature name Enforcement Evaluation Subscription Enabled RightToUse 
appxk9 yes yes no no yes 
uck9 yes yes no no yes 
securityk9 yes yes no no yes 
ipbasek9 no no no yes no 
FoundationSuiteK9 yes yes no no yes 
AdvUCSuiteK9 yes yes no no yes 
cme-srst yes yes no no yes 
hseck9 yes no no no no 
throughput yes yes no no yes 
internal_service yes no no no no

The licensing magic trick? Configure the platform to jump from 200 Mbps to 400 Mbps:

Router(config)#platform hardware throughput level 400000 
% The config will take effect on next reboot

Upon rebooting, NOW the throughput license is enabled.

Router#sh license feature
Feature name Enforcement Evaluation Subscription Enabled RightToUse 
throughput yes yes no yes yes

Router#show platform hardware throughput level 
The current throughput level is 400000 kb/s