Balancing RM over Big -Ip LTM F5

Have anyone configured something like this recently?
A pair of Resource Manager ver 8.5.130.58 working balanced over a BIG IP-LTM versión 11.6
I have it working over another group of servers in versión 8.5.001.89 but now i am trying to do it with the versión 8.5.130.58 and i haven’t suceed. Basically my problema is that the sip server requests does not reach the Resource Manager, my provider which is my directly technical support have not help me a lot to get around this, so if you have any ideas it would be great.

thanks in advance

As first you have to check it on F5 level.

PS: Why do not you use the SIP server as LB?

Yes i have now open a case with f5 support and we are working together.
The idea you gave me is great and really the workaround for the problem. it would try to make the solution to work over f5 for two week more if it is not possible then i would use your advice. Thanks