This guy shows you how to use washers and epoxy.
I added wood to my guitar so that I could remove it easily if I wanted.
These two options are very inexpensive.
This link has much info on floating trems with some blocking techniques with pics if you scroll down.
Two other options are an Ibanez backstop and ESP Arming Adjuster.
The backstop was only available with the guitar in the 80's. I got one with a 540R I got off of ebay.
Steve Vai uses one for his live performances. They are very expensive if you can find one. I sold mine for $200.
There was a guy in Canada who was selling the ESP on ebay for around $60.
The Ibanez is a superior product.
I haven't tried a Tremel-No, but it looks like it would work well and it does not alter your guitar.