I’m curious, are the strip sizes uniform across ranges? I’m currently painting Napoleonic British, and it looks like the strips are 18mm. That’s leaving me with a bit of a basing dilemma. In a perfect world I’d love to do 20mm or 40mm wide bases with minimum gaps for that continuous line look. Anyone have any advice for me? What’s the reasoning besides the slightly smaller strip size?

You don't have to base in strips. Our patent sprue cutters make it easy to separate them.

https://baccus6mm.com/catalogue/BrushesPaintsandtools/

The strips should all measure 20mm.  However, until recently these were done using a technique which could produce varying results, slightly over and under the nominal width.   All releases from late 2018 onwards have been produced using a standardised method which will yield consistent and accurate strips.

The staff here, all of whom have engineering backgrounds, put this down to letting a man who has an arts degree do all the strips prior to 2018.    They regard this as a problem.  I have informed them that they must let the Creative types have their way.   I will let you make your own judgement...

Ah yes, I see that now. My WSS strips are 20mm on the dot, my British Napoleonics are 18mm. Is it safe to assume that the entire British Napoleonic range is similarily 18mm? Looks like I'll need to get creative with basing. On a 40mm base if I cram in an extra guy that should take up the space.  It's probably best to clip minis before painting them eh?

I clip them before and glue them to a tongue depressor with wood glue to paint them.  They easily lever off the wood to be stuck to the base. 

'Is it safe to assume that the entire British Napoleonic range is similarily 18mm?'

Sadly, the answer is 'No'.   Due to the way that the strips were produced there may still be small variance between codes.

If basing by the unit, it shoudln't be a problem. You'll have at most 3mm at either end of the line (assuming you're basing in 2 ranks of 3 bases). If not basing by the unit, then some snipping maybe required to space the little men out a touch. Snipping should be done prior to painting. However, it's do as I say and not do as I do as I often snip after painting!

That’s my dilemma. I’m using multi base units. I’ll try cramming 9 guys into a 40mm strip. I’ll need to shave off 0.5mm of the other strips, and add an extra guy. The downside is a bit of fiddlyness and an extra 6 guys to paint per base. The upside is that the unit will look even better, a single solid line, two ranks of 27, standing elbow to elbow!