I think you have these options:

1- Reversing Y-harness. This will work but you'd better have the linkages close to the same since you won't be able to adjust end points or trim on the servos individually. http://www3.towerhobbies.com/cgi-bin...&I=LXAFN2&P=ML
2- Match box. this is similar to a reversing Y but has the abiliity to control centering and end points. http://www.horizonhobby.com/Products...ProdID=JRPA900
3- Use separate channels for each servo and mix in the radio. One servo will go into the regular elevator spot on the Rx and the second will go into an unused channel. You use a programable mix in the radio make the servos move simultaneously. This way you can reverse either servo as needed, control end points, trim, etc. individually.