migrating from Siebel 7.7 SEA to siebel 8.1.1.11 SIA in two steps

We are migrating from Siebel 7.7 SEA to siebel 8.1.1.11 SIA in two steps;
First step we are migrating from Siebel 7.7 SEA to Siebel 8.1.1 SEA;

Second step we are migrating from Siebel 8.1.1 SEA to 8.1.1.11 SIA ;

At second step , is it possible to apply 8.1.1.11 FP as a patch, followed by IRM , even if we are at SEA ?

Or is it better to install new version 8.1.1.11 and make the traditional upgrade process from 8.1.1 SEA ?
In this case will we have to execute Incremental Repository Merge (IRM) at what moment ?

Thanks

Jose Alexandre