V6 Headgasket - Flush fit?

[s3swiss]

Just tried fitting my Partco supplied headgasket over the weekend and was surprised to find it 'bowing' upwards in the middle when fitted into position over the 2 headbolt lugs(ie lifted off the block by about 2-3mm over middle cylinder). Previous engines I've worked on have always had the gasket lie nice and flat on the block ready for lowering the head onto it. I've popped the gasket back and asked them to contact the manufacturer, but in the meantime - anyone else had probs with apparently too big headgaskets? The gasket set is manufactured by 'Ultra-Parts' and also contains a rather flimsy inlet gasket (compared to the more substantial Ford item removed). Cheers all.