I have successfully built contour map for Spain using srtm2osm -> splitter -> mkgmap. I combine srtm img's and regular map img's with mkgmap. Up to here everything goes fine. The problem now is that major and medium contour lines are shown at any zoom level in MapSource and gps, not taking into account resolution established in style (see below). It makes rendering really slow when you zoom out and all the map is covered by contour lines. Minor contour lines do appear at the right zoom level (1.5 km in MapSource). The problem is in the contour map, because it's the same if I only install it (without regular map).
Contour lines style used:
contour=elevation & contour_ext=elevation_minor
    { name '${ele|conv:m=>ft}'; }
    [0x20 resolution 23]
contour=elevation & contour_ext=elevation_medium
    { name '${ele|conv:m=>ft}'; }
    [0x21 resolution 22]
contour=elevation & contour_ext=elevation_major
    { name '${ele|conv:m=>ft}'; }
    [0x22 resolution 20]
Commands used:
*srtm:
mono Srtm2Osm.exe -bounds1 35.99 -9.501 43.79 4.33 -step 10 -cat 100 20 -large -corrxy 0.0005 0.0005 -o srtm_peninsula.osm

*splitter:
java -Xmx2500m -jar /home/carlos/Paquetes/mkgmap/dist/splitter.jar --mapid=63240101 --mixed=yes --cache=/160GB/cache_srtm/peninsula/ --max-nodes=5000000 --split-file=areas.list srtm_peninsula.osm

*regular map:
time java -Xmx600m -ea -Dlog.config=logging.properties -jar mkgmap.jar --generate-sea=polygons,extend-sea-sectors --route --latin1 --code-page=1252 --gmapsupp --series-name="OSM-Iberia-n" --index --road-name-pois=0x640a --ignore-maxspeeds --remove-short-arcs --add-pois-to-areas --adjust-turn-headings --report-similar-arcs --link-pois-to-ways --location-autofill=1 --drive-on-right --check-roundabouts --check-roundabout-flares --style=mio --delete-tags-file=quitar_is_in -c spain.args

*contour map:
family-id=36
product-id=1
family-name=Curvas nivel Península
series-name=Curvas nivel
area-name=Península Ibérica
draw-priority=28
transparent
style=srtm

mapname: 63240101
description: SRTM-Iberia-01
input-file: /160GB/Srtm2Osm/63240101.osm.gz

mapname: 63240102
description: SRTM-Iberia-02
input-file: /160GB/Srtm2Osm/63240102.osm.gz
...

*final join:
java -ea -jar mkgmap.jar --gmapsupp --family-id=35 --product-id=1 --family-name="OSM España" ../mapas/curvas-es/6324000*.img typ/SPAIN-35.TYP --family-id=36 --product-id=1 --family-name="Curvas nivel Península" ../mapas/curvas-es/632401*.img