Note! Before doing ANYTHING in Sketchup, import your own textures on to it. Don't EVER use the default textures. The reason: every time you paint with default Sketchup textures, it makes a new material. That is a new material to every non-divided surface. You'll easily end up with hundreds of materials and the game says then "noooooo..." First, do a texturepack containing basic colors, 32x32 pixels is the minimum size, use that in every new design. You can change the textures after 3D shape is formed. SU won't show how many duplicates it uses so you have to manage that yourself.
I don't know if it is only SU6 that does this but SU wasn't designed for modding and games. Later, you may need to draw lines to make the polygons like you want them to be, they are not optimized for games or further modification in mind. When doing SObjects that use "vertices follow the ground" you pretty much have to draw every vertice by hand. Fortunately, those objects are lopoly anyway, so it is not a big deal but a necessary process. You can check how the actual shape is formed by importing an object to BTB and vieving it with wireframe mode (W cycles the different view modes). The choices that SU makes are not always what you would think they are.
Also remeber to paint the reverse side of faces with a texture that is used somewhere in the model, use Shift+Click to paint all of them at once. The reason: if you don't, you'll end up with one unused texture (ForegroundColor) that neither the game or BTB uses. This is probably to make SU exported dae files compatible with SU.. Weird but true.. There are some track out there that have blank duplicate textures because of this. You cannot delete that texture in XPacker as it is still asigned to the model, you have to do it in SU.
EDIT: more tips... Design the basic shapes not using the "Shaded with Texture" but in "Monochrome". That way you see when SU decides to reverse a face.. That can happen anytime. I've had reverse face appear with single flat quad and inserting a new vertice (line). It has some sort of algorithm based on the direction of the line drawed and to this day i haven't been able to figure it out. But for ex, if you draw a single flat circle, it is reversed (SU expexts that the newly formed circle is going to be expanded to 3D shape, ie the formed circle is underside of object. Very frustrating and it happens all the time so at least check once in a while how the faces are arranged in "monochrome" view mode.
Hehe, wish me luck! lol
