Stoo suggested that it might be that exact problem. I brushed him off thinking it was impossible, because the port itself is black (not letting in any light), and the space between the lens, and the port body is soooo small that I figured it was impossible that was causing the issue.
But now here you've confirmed that it may just be that. Of course, Ikelite will not admit to that! Their housings are just perfect!
A friend of mine had a similar problem. At my urging, he posted here...
In summary, there were two things going on... At the heart of it though, was strobe positioning. If it/they are too far forward, it really exasperates the problem it seems. I little experimentation might help.
Personally, I hate the thoughts of sticking Gorilla Tape or anything else on a lens. The things are works of art and this just seems abusive.
Congrats on the new system. I shoot with the same camera and 161s. I added a second 161 a few months after I got my last camera. It made a significant difference in my images... Not only with WA as you would expect, but also with macro... More even lighting, shadows eliminated etc.
I don't think you would have any issues with using a DS25. I rarely have my strobes set at more than a little over 1/2 power as it is. I really prefer subtle lighting... I'd stick with Ike though... Just so they look like they go together!
Some companies just "get it". You're now a loyal customer for life. You have told a pretty targeted audience about your experience, and this will undoubtedly result in more sales for them. But that probably wasn't their motivation for replacing the light. Good people, making great products tend to do the right thing...