Yes. I mentioned that as being my prediction as well which is why I purchased some spare lens tubes. I will increase the opening size in the nozzle.
Also, a 4" FL lens actually engraves exceptionally well. I have been surprised. I have plenty of 2.5" FL lenses and thought by now I would feel that I wanted to use them, but seeing the result of the 4" FL, I haven’t found it necessary to swap out the lens.
Another reason I got spare lens holder tubes (that have cones and air inlet quick connects), however, was to have readily available different focal lengths that are very quick to swap if needed. I know for certain that a 2.5" FL is not so good for 1/2" or especially 3/4" cutting. But there may be times I want to really have fine detail engraving. That will be when I could use an even shorter FL (maybe 2" or 1").
And I also had mentioned that i recognize the air assist would be compromised, but some of that I may easily be able to compensate for. Hey - It’s all in the name of experimentation.
Here is some engraving with a 4" FL that really came out well. This type of work not needing extreme resolution (I hadn’t yet wiped off / polished the ghosting off, so don’t hold that against me):
