Canon Selphy printer series and natural size printing

Many times I tried to get natural size prints with my Canon Selphy (CP 710 model) but there was no way to get it!
Printer's specs are simply 300x300 DPI on a standard Canon Color Ink/Paper kit 4x6in (100x148mm) format.
Everybody would think that it's easy to do by setting up a 4x6in image @300x300DPI and printing it borderless but result is far away from a real size printing!!!
Where is the problem with this printer series?If you look at a borderless print that it takes the full printable area you will see that picture goes out of pre cut paper area.
Lets take the lenght of picture and you will see it is 152,75mm long to be as sharp as possible with my digital calliper.
Really the maximum printable area is not 148mm but 152,75.
So to get a ntural size print we must create an image 100x152,75mm @ 300x300DPI borderless taking in mind that we will loose respectively 2mm on side up and 2,75mm on side down cutting sides away (152,75- 2 -2,75=148).