FWIW, when our daughter was starting at age 3.5, she was about 41'/39 #s and did great on 80 cm skis. Last year, she was on 93cm skis at about 43"/41 #s and age 4.5. I didn't think 13 cm was a big jump for her.
After making the change, I could see how the 80 cm skis might have slowed her down a bit. That said, she's a pretty coordinated/enthusiastic little kid, so YMMV depending on how coordinated/enthusiastic your child is.
Dino, thanks so much for taking the time to answer.
My kid is pretty motivated, and has decent coordination. Skied for 4-5 hours with breaks last time out too. By "slowing down," did you mean slowing down skiing speed on the hill or slowing down her progression? Sorry, I sort of got it... 13cm might not be too noticable to the kids, right?
I've been keeping my son(now 5) on skis that stop somewhere in his lower face for length for the last 3 years. I think too short a ski can cause problems too. he may over ski (go faster) than the short ski can control. I think more edge allows for more stopping power especially in a wedge. I would suggest trying his on the longer skis and If it doesn't work out go in and rent. Just make sure his bindings are adjusted for his boots and weight. also make sure they are tuned and waxed. some think it is a waste to tune and wax kids skis but waxed skis let them slide easier on the low angle slopes and a sharp edge inspires confidence in the turns and especially stoping.
Sternum is too short, IMO. Skis will be easy to turn, but unstabile if he gets moving and hits an irregularity. Our level 3 5 year old has been on hand-me-down skis that come up to there, his instructor told us recently that he should be on a length that touches bottom of chin. Once they're intermediates, the line goes up to the mouth.
Yes, I've been going with chin height to just below the nose length skis for our daughter.
I felt if they were shorter than about chin height, then the effective edge would be too short and/or fore/aft balance would be tougher.