Never used perfect world, I just use the built in stuff. Took a while to figure out though.
Too long to explain here really. I posted a commented version of my pocket region generator of choice for my personal use recently, I'll see if I can dig it up, it will perhaps help you understand how the worldgen works a bit better.
I don't claim to know it extremely well, but I know it well.
*wanders off to search through old posts*
Here's an example that generates extremely volcanic 17x17 regions.
[TITLE:POCKET REGION]
[DIM:17:17]
[EMBARK_POINTS:1274]
[END_YEAR:1050]
[BEAST_END_YEAR:1000:80] *give plenty of time for erosion to work - erosion every year
[REVEAL_ALL_HISTORY:0] *I'm not interested in how many times Urist's cat killed rats
[CULL_HISTORICAL_FIGURES:1] *I'm not interested in what the mayors of long dead towns did
[ELEVATION:1:400:10:10]
[RAINFALL:10:100:10:10]
[TEMPERATURE:35:65:10:10] *slightly raised lower limit & lowered maximum limit.
[DRAINAGE:20:100:10:10] *I believe higher drainage = more soil & fewer aquifiers.
[VOLCANISM:30:100:10:10] *Volcanos are good
[SAVAGERY:0:100:26:26]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[MINERAL_SCARCITY:100] *I refuse to generate worlds without tons of metal it.
[MEGABEAST_CAP:1]
[SEMIMEGABEAST_CAP:2]
[TITAN_NUMBER:1]
[TITAN_ATTACK_TRIGGER:80:0:100000]
[DEMON_NUMBER:20]
[NIGHT_CREATURE_NUMBER:20]
[GOOD_SQ_COUNTS:1:0:0]
[EVIL_SQ_COUNTS:1:0:0]
[PEAK_NUMBER_MIN:0] *World gen doesn't like lots of mountain peaks AND lots of volcanos.
[PARTIAL_OCEAN_EDGE_MIN:0] *Why would I want water? Undrinkable water?
[COMPLETE_OCEAN_EDGE_MIN:0] *Why would I want water? Undrinkable water?
[VOLCANO_MIN:25] *I want volcanos! Volcanos I say!
[REGION_COUNTS:SWAMP:0:0:0]
[REGION_COUNTS:DESERT:0:0:0]
[REGION_COUNTS:FOREST:0:0:0]
[REGION_COUNTS:MOUNTAINS:0:0:0]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:1] *erosion every single year makes fewer nasty cliffs - especially after a long history.
[RIVER_MINS:10:9]
[PERIODICALLY_ERODE_EXTREMES:1]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:2750]
[CAVERN_LAYER_COUNT:3]
[CAVERN_LAYER_OPENNESS_MIN:0]
[CAVERN_LAYER_OPENNESS_MAX:100]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:100]
[CAVERN_LAYER_WATER_MIN:0]
[CAVERN_LAYER_WATER_MAX:100]
[HAVE_BOTTOM_LAYER_1:0]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:15]
[LEVELS_ABOVE_LAYER_1:5]
[LEVELS_ABOVE_LAYER_2:1]
[LEVELS_ABOVE_LAYER_3:1]
[LEVELS_ABOVE_LAYER_4:1]
[LEVELS_ABOVE_LAYER_5:2]
[LEVELS_AT_BOTTOM:1]
[CAVE_MIN_SIZE:5]
[CAVE_MAX_SIZE:25]
[MOUNTAIN_CAVE_MIN:1]
[NON_MOUNTAIN_CAVE_MIN:2]
[ALL_CAVES_VISIBLE:1]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:5]
[TOTAL_CIV_POPULATION:15000]
[SITE_CAP:18]
[PLAYABLE_CIVILIZATION_REQUIRED:0] *I don't really try for no dwarf worlds, but leave the option open.
[ELEVATION_RANGES:36:72:36]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]
Also note that I modified variance numbers down for a couple entries. The lower the variance, the slower terrain is to change. Specifically I think I modifier elevation, drainage, and volcanism.
The above settings generated one of the best maps I've ever seen in DF -
http://dffd.wimbli.com/file.php?id=4521But for your purposes you might want to adjust number of volcanos down a bit, and maximum elevation down as well, then drop variance even further. Be prepared for many fails, but you might eventually get what you want.