Light twin pilot reports near runway incursion from Taxiway A onto Runway 7 at GNV due to poor hold line markings and confusing juncture of Runways 7 and 11.

Narrative

Ground control instructed taxi to Runway 7 hold short of Runway 11 approach (has red sign indicating Runway 11 approach). While holding short of Runway 11 approach; tower instructed to taxi to Runway 7. The taxiway curves from that point and without being familiar; it is almost impossible to determine from the NOAA airport diagram that there is or is not an additional holding point. As it would not make sense to issue a taxi clearance past that point unless there was another holding point; pilot assumed as much. Runways 7 and 11 begin almost at the same point; however there is access to Runway 7 without crossing Runway 11. In addition; Controller changed runway assignment twice. Began taxi past Runway 11 approach point and noticed runway edge markings of Runway 7 and aircraft on short final. Stopped prior to runway incursion but feel that this is a very dangerous situation. ATIS has standard message about read back of hold short instructions; but no mention of this specific safety issue. Nothing in NOTAMs.