you could make the terrain repeat a bit and release this is a gmod map...
No problem, easy fix up. I might add caves too for, you know, exploring.
That's nice, You could soften up the ground a bit. The airboat was jumping a bit.
I was trying a little to hard to resemble the original slopes, since physical interaction and collision is a tad different in the Source Engine, it made this look and feel rough.
I would defiantly smooth these areas out and also fix some of the spike-y unrealistic areas.
Maybe also add in more detail to the slopes like rock cliffs and pine trees if that's for any confort.
I'm not quite finished with polishing it up, hence how the whole thing was composed of one non-blending texture and some water. I'll redo the texture port and add in some of the rocky/icy textures the original Slopes had.
EDIT:

Fail Mod: Blockland Source!