[racket] racket 5.2.1 and 5.3

Hi,

I was not following closely the latest developments, but
I have just tried version DrRacket 5.2.1 and 5.3 on Windows 7, 
the 64 bit version, and I have noticed two things:
- In version 5.2.1 for the canvas% the (send this get-scroll-range 'vertical) does not work. It simple
fails. No other error message. I was trying to run the MrEdDesigner program. (It could be my fault, I just wanted to mention.)
- More importantly in version 5.3 what happened to mrtabgroup ???
How do I create tabs?

Thanks,

Peter Ivanyi