Hi Dan,
Here is a picture of a GT caught on a 140g Bigfoot just south of Tantabiddi. The 190 is not much bigger but is significantly heavier than the 140, and therefore sinks alot faster. I wouldn't recommend using the 190 up around Exmouth - apart from the increased effort required for each cast, alot of the area around Peak and the Murions is very shallow. You wouldn't be the first angler to have his Orion BigFoot snagged onto the bottom, and not the first to have to dive in to try and retrieve it either.
The Big Foot is fairly simple to work, and being a sinking stickbait, this makes it even easier!. I think the T-Curve will be able to work it fairly easily.