Hi Sue,
How do you know he was in Tas in 1834? Did he get married or have children?
If he was a convict then he would have had to apply for permission to marry, so there should be some paperwork dealing with that, but the Tas Archives index shows nothing under the name VIMPANY. The only VIMPANY showing on their convict index is Charles.
He may have gone to Tas to be with his (possible) brother, and/or on one of the British government immigration schemes. My own g-g-g-g-grandfather and his family came to Tas in 1832 on such a scheme, for Chelsea Pensioners.
Prue