Install URL Rewrite module and put something like this in the ROOT web.config of your web server:
<rule name="Rewrite SP4 URLS to SP5 URLS" stopProcessing="true">
<match url="^tenantA$|^tenantA/$" />
<action type="Rewrite" url="/SP5_ssp_root/tenantA" />
</rule>
add 1 per SSP (or invent some clever regexp to handle more than 1 old ssp)
BR
Peter