THEMA: HELP!!! Simply question How to remove bumps?

Hello again!
(Now i ll ask simple question. My previous question about DCC was complicated, sorry. )

------------

I reconstructed my layout once more, removing other problemms.

But one problem still remains:
It's a small invisible plywood bumps between webbings, due to tension of plywood at curved slopes.

This picture imagine the part of my layout and the principle of such bumps:

http://img-fotki.yandex.ru/get/4001/vadimav.0/0_30afa_afa05605_L

This bumps obviously lead to derailment.

These bumps still remains, even i make all webbings with high accuracy.

Layout DATA:
Slope = 2%
Plywood thickness = 6mm
Distance between webbings = 15 cm
Webbing thickness = 12mm
Turning Radius = 32 cm

Question: How to remoove these bumps?

May be these abrade device can help? :

http://www.makitapro.ru/u/catalog/106-bo3700_l[1].jpg

I think, there are some  people who encounter with this kind of alterning rare hellish derailments due to such bumps.

Which way of solving this problem?
May be some standard tools exists?
-----
Vadim