I've built around 60 instruments with hand tools, so I've worked through everything posted since I last commented.
1. Of course I know how to use a cap iron. But hogging off 2.5mm that way takes forever! The cap iron limits the shaving thickness. Planing cross grain allows much thicker shavings with minimal tearout.
2. A scrub is quick, but I have two issues. First is holding the work - I need to scrub at different angles, which means a lot of time repositioning. Second, heavy tearout, especially on figured wood. I can't risk scrubbing down to even 3mm if I might get tearout deeper than 1 mm. So I can scrub from, say, 5mm to 3.5 mm, but after that it's slow going.
I'm looking for something to reduce the grunt work. The proper tool is a drum sander, but I haven't the space and making 2 or 3 a year doesn't justify the cost.
So far my options seem to be belt sander (40 grit belt should make dust pretty fast) or a decent hand electric planer used with great caution.
The final 1mm or so is removed using hand planes with a close set cap iron and/or card scraper, with lots of pausing to flex and assess the plate. I'm not trying to achieve a consistent thickness, because each square cm of the plate needs individual attention.
It's the first 2.5 mm which I'd like to remove with least effort.