Your first mistake was buying the mounting bracket (mine too) the thing interferes with you actually using a water bottle in the other position (at least on my bike) and I found that that position didn't aid me in the slightest as when I needed to mount the bike on a bus rack I felt it necessary to remove it lest the lock be jarred loose. I simply place it in my messenger bag in an convienient spot and have had no troubles.
I personally haven't had the problems you describe with attaching it to an object with the intent of locking up the bike - sure it's one extra twist of the key but as long as you took the time to position the keyholes where you have easy access to them (takes a second of forethought) it's not that big of a deal.
One thing puzzles me.
My city requires that bikes have s/n chiseled into frame. This is place for corrosion to start (yes I can paint over) and voids lifetime warrantee of this particular frame
I presume that s/n means "Serial Number" is the serial number of the bike not engraved at the factory or do they issue you a registration number that must be engraved? If this is the case you may find that anybody else's registration process will demand the same information be provided meaning you'd be ass out anyhow. Lock warrantee's generally pay for the deductable for your bike on your homeowners / renter's policy which your bike should already be listed on.
One added benefit - Street Cuffs are an excellent visual deterrent! People see them and are reminded of their cousins - police hand cuffs it tends to keep honest people honest. Edit: 3-23-05 Street Cuffs suck Endorsement rescinded