InRoads ITL & IRD Files - XM and V8i

IR XM & IR V8i SS1
One of our users has very large template and corridor libraries. The ITL is 50 meg and the IRD is about 48 meg. In InRoads and MicroStation XM, we get out of memory errors when these are opened and applied.

In InRoads and MicroStation V8i SS1, I can run them lickety-split. No problems. We realized that there were a lot of unnecessary display rules in the template library, and it was a lot easier for me to identify them and delete them in V8i (even though I had to view each component in the Active Template tab).

In V8i, when I apply the skinnier template library (without the display rules) to the IRD, that file size is reduced substantially. But when I apply the slimmer template to the IRD file in XM, it doesn't change the file size. I even tried to create a new blank IRD file and import the updated template drops, but it still does not reduce the size of the IRD.

Has anyone noticed differences with their template and roadway design libraries between InRoads XM and V8i SS1? Does anyone have an explanation about why the V8i IRD file compresses, but the XM one does not? It kind of appears that these libraries compress as soon as they are processed in V8i.  Since there is no file format difference, I'm assuming that these files can be used interchangeably between XM and V8i, right?

Thanks in advance...