Meanwhile, most keyboards (especially desktop boards) have spacebars so wide that none of the modifier keys are easily reachable by thumb. C through M should be the widest allowable spacebar, and splitting it is great.
I'm typing this on a Unicomp Model M-compact clone, an Ultra Classic. The spacebar goes from C through just past M and into ,. Buckling springs and a reasonable ($79) price.
The one thing I wish I had though, was a laptop with a split space bar. Thumb delete is the best keyboard innovation in like 20 years.