The modification almost doubles the time you can use the batteries between charging.
It is a fairly easy modification and has been done by some of the Naples sailing group and others.
Rob Guyatt (RMG winch)has also made this modification and says it works very well.
To make what you can see in the link above easier, somebody suggest to cut the leads off the original regulator, leave them on the board then fit the leads of the new regulator to them and sold in that manner. Any objection?
Why do you think the engineers who designed the TX went with a linear regulator and not a switcher? I would be willing to bet money that it was because they didn't want the RF noise that a switcher produces because it would interfere with the TX output. Personally, if battery life is a concern, I'll spend the $20 on another TX battery.