Hi Mike,
we have a solution to help control the height and width and will be releasing this soon as its needed for our add-ons. I created a quick sample using your rich text formula code and incorporated that into our solution and it works fine. So we can use a formula rich text formula field like in your example or a standard formula url field which is what our add-ons are installed with.
See the quick snipped attached. This is using your formula rich text code and our solution.
(click the "view attached" above...the animated gif below doesn't really work well)
Keith
------------------------------
Juiced Technologies
Juiced Technologies, Inc.
631-617-5060
------------------------------