I've never used Splenda in mead - or anything else for that matter - but I do know that a lot of cider makers use it to back-sweeten hard cider. Do a search on one of these forums for a TON of info on Splenda as used as a back-sweetener:
http://tinyurl.com/yqnahu
http://tinyurl.com/289pyu
http://tinyurl.com/yq7bvv
Good Luck!
- GL63
http://tinyurl.com/yqnahu
http://tinyurl.com/289pyu
http://tinyurl.com/yq7bvv
Good Luck!
- GL63