2008 Tacoma with factory tow package - tongue weight questions

I am looking at the hitch mounted toy haulers. In the metro NY area, we have a lot of tolls. If you tow a trailer, you have to pay much more than if you just have your vehicle. When heading out for a quick solo ride in the dirt, one of those hitch mounted single dirtbike haulers look like a good option. i could get ramps and just drive it into the bed, but that would require removing the cover every trip. And thats not something I want to do.

http://hitchcarriers.com/index.php?...category_id=45&option=com_virtuemart&Itemid=1



These items are what i am thinking of. I think between the weight of the bike and the weight of the acutal bike holder, it would be ok.

I read some where the tongue weight on the 2008 with the factory tow package is 650#. So does that mean i could install this carrier (weighs 40#), and put something that weighs up to 610#?
Disregard the fact you can only hold a bike that weighs up to 400# on this carrier....im talking about the hitch and the capacity of the hitch only.

I am not familiar with the tongue weight, but i think it mean the combined weight of what ever you plug into the hitch receiver and the item sitting on it. Is that correct?

Lets assume the bike weighs 200# (its a little under) and the weight of the carrier is 40#.....i shouldnt have a probolem plugging that into the Tacoma's hitch and heading out right?

Any suggestion on beefing up the rear shocks for the added weight?

Any reason to think the weight beign so far to the rear that it could cause premature wear on the rear suspension components (shocks for example)?

Any advice on preventative measures if this setup is a go?