HI TP,
When you say summarize SPL, are saying to do by OBCY? I only know this summarization in FI. SAP offered summarize in the CO component but I don't think so it is your idea.
If you summarize you'll save space in the table and performance will be better but you don't have a lot of analysis in the reports. And normally these posts doesn't represents so much space.
So, in my opinion, I don't recommend.
In the past I worked on project and the wanted to summarize cost center to save space. But after years they asks to undo because they did a lot of posts and they can't do analysis these cost centers.
JPA