Passing dtsconfig from Master to Child packages

Hello all, I am new to SSIS and have inherited a solution which has roughly 30 packages in a solution. I have lost a week trying to resolve this using the power of Google and ameteurish experimentation. I realise I could spend more time eliminating possibilities but was hoping someone might help me shortcut that a bit.

Problem; I am trying to create a master package for a solution containing about 30 packages and over a week have failed to be successful. I want to pass the location of the dtsconfig file from the parent to the child but the child ignores it. From what I have read, I think this should be possible but just can't make it work.

Scenario. I have a solution which is housed in C:DevelopmentSSISJPMC POC DEV1. the solution has roughly 30 packages that all use the same dtsconfig file housed in the above path. They all leverage tables in the same DB JPMC_POC_DEV1. To develop changes, I copy the entire solution to a new folder e.g. C:DevelopmentSSISJPMC POC TESTING and create a copy of the DB calling it JPMC_POC_TESTING All 30 packages have the same connections so I edit the new dtsgconfig file in two places to point the Package connections to the new JPMC_POC_TESTING database. Then I edit each of the 30 packages to point it to the newly edited C:DevelopmentSSISJPMC POC TESTINGJPMC POC Configuration.dtsConfig All the packages are currently run individually. When I am done testing I have to repeat the above to put it back in the original folder.

ISSUES; What I think I want to do, is create a master package to run all the 30 packages and pass them the location of the dtsconfig file. My intention being that I only have to change the dtsconfig location once in the parent when I am moving between C:DevelopmentSSISJPMC POC DEV1 and C:DevelopmentSSISJPMC POC TESTING.

So Currently I have a master package (MASTERPKG) and have given it a string variable called CONFIGPATH at the package scope level. I have entered "C:DevelopmentSSISJPMC POC TESTINGJPMC POC Configuration.dtsConfig" in the variable. In MASTER there is just one "Execute package task" which calls one of the packages called "DIM_HEADCOUNT". In DIM_HEADCOUNT package, I have created a string variable also called CONFIGPATH and set the Package Configurations to use "Parent Package Variable" and use the Parent CONFIGPATH to set the Value property of the DIM_HEADCOUNT CONFIGPATH variable. When I execute the task from MASTER, the child package completes using whatever connections were already defined and does not use the new connections defined in the parent dtsconfig.

OBSERVATIONS; In the solution there are 2 datasources ("Target OLEDB JPMC DW" and "Target .Net JPMC DW") and every package in the solution has 2 Connection Managers with the same names.

QUESTIONS; What am I doing wrong? Is what I am doing possible? Do the Solution Datasources and Package Connection Managers duplicate each other and/or override each other in some way causing it to appear that the config file is being ignored?

Thanks. Dan