Hi, may not be the perfect solution but my son used to have the same problem with his shin guards so I started putting talcum powder onto the EVA before he played.
Worked for him as I guess the talc soaked up the sweat (yueck!) and reduced the friction.
Did ask around for EVA free guards but was told of some horrible injuries when people removed the `spongy bit` and the shin guard splitting and embedding in the skin so thought it best to stick with the talc!!
Hope this helps
Juls
This item was edited on Sunday, 7th May 2006, 22:12
I had similar problems and my mam used to put shed loads of talc then a loose tubigrip/long john type thing on my leg, then the shin pad and socks holding it up onto my legs, it was a pain to do and had to be prepared before the game but it was a huge help, at the very least talc is a good idea because from experience it was the sweat and friction that caused the probs.
I would also say a big no-no for unpadded shin guards, all it takes is one bad tackle or bad fall and the plastic can cause some serious damage!
All though i`m sure some of the `oldboys` will reply soon talking about the days before shinguards, offside rules and jumpers for goalposts, when men were men... ;) 
This item was edited on Monday, 8th May 2006, 00:11
Adidas do the all-in-one shinpads with ankle supports that have a material backing. I am sure that they do them in youths.
Cheers
Nick