seating plan zoom feature consistently used the slider control

Currently if a room has 50 possible seats or fewer, then the seating plan dialog has the ability to zoom the seating plan from 50% size to 150% size using a continuously-variable slider control (as shown in the module documentation).
However, for rooms with 51 or more seats the zoom feature only has radio buttons for three fixed zoom levels: 50%, 100% and 150%.
This is not only inconsistent but a real inconvenience as the 50% zoom is generally too small to be readable for larger rooms, thus forcing scrolling about the plan as an intermediate zoom level is not selectable.