Issues by same reporter in custom field / Performance

[Bob]

Dear helpful people,

I'd like to create a little overview of other issues created by a specific reporter and display this in a custom field. 

I managed to do so using Scriptrunner and a Script Field. I run a JQL search, gather the results, take the 5 newest issues, run them through MarkupBuilder to display them in a pretty way.  

So far so good. 

At his point, however, I'm already a bit worried about the impact of the field on the performance of my JIRA instance. 

These worries are enhanced as I put things to the test and add the script field as an issue navigator column. Things come to a grinding halt. 

What options do I have to make this work?

I've already reduced the scope by limiting the fields configuration scheme context. 

Can I prevent the field from being added to the issue navigator? Am I missing other potential risks when implementing this approach?

Or is there perhaps an altogether more elegant way of getting the same results?

Thanks in advance!