Spline Modify: keep geometry length

The Spline modify tool is very powerful, but it doesn't allow to do one particular thing. If you have an object that you need to bend and keep its length at the same time, you currently cannot do this easily without carefully tweaking the path curve to a length equal to object's length (by monitoring spline length in Object Explorer) or by eyeballing it while fiddling with percentage slider in the Spline Modify window.

I'd love to see some sort of a checkbox that would force the deformed geometry to keep its length.