There are several ways to do this without a better TX, but none of them are satisfactory IMHO.
If you are getting into planes that require this type of set-up now, why don't you just "bite the bullet" and upgrade your TX? Keep your current one as a back-up or trainer TX, or sell it.

I just think you will be much better off with a TX that is up to the task, rather than trying unsatisfactory fixes.

While you are at it, buy a TX that will last you a long time so you won't ever need to upgrade again in the future. If you plan on getting into 35% or 40% planes eventually, buy the top of the line TX and it will serve you well for a long time.


Jim