What kind of bow are you trying to make ? A horn wood sinew composite,or one of those gemsbok self bows ?
If it's a composite ,just cut both strips . And thin them to the same thickness ,other than removing the ridges and general shaping , I remove most material from the inside side.
If you are making a self bow ,Yes you can tiller it,just scrape from the belly and the back . And check with a coat hanger ,for the amount of solid horn in the end of each horn ,try to use two horns with about the same amount of solid ends . (like with american bison male and female horns are a little different ,and have quite a bit of difference in the proportion of solid to hollow horn )
Ralph