FAA/TSA Question

[Tootles the Taxi]

I've spent some considerable time utilising the search function which has yielded some useful material but perhaps someone would be kind enough to help me with this one:

Going through the licence verification process to get an FAA Private on the strength of a JAR Multi-Engine CPL/IR with SE Class Rating with a view to then training for a ME Commercial with Instrument. Regarding TSA approval, I've looked through the TSA AFSP guidelines and understand that I am required to obtain a TSA Approval for an Initial airman's Certificate, instrument and muti-engine rating however, I believe that I am eligible for instrument and multi-engine priviledges attached to my Private issued on the strength of my JAA licence. If so, am I still required to go down the TSA Approval route or can I simply proceed with multi-engine commercial training without TSA involvement and if so would my foreign based IR carry across if I do the Instrument approach on the multi-engine commecial checkride - or am I completely barking up the wrong tree in an attempt to save a few dollars?

Many thanks for any response - apologies it's a long one!

[B2N2]

would my foreign based IR carry across if I do the Instrument approach on the multi-engine commecial checkride

No, you foreign IR does not carry over to a US CPL certificate.
It's meant to do recreational IFR flying in the US.
You'll need to take the IFR written test an a check ride with a US examiner prior to undertaking the CPL training.
So you still need TSA for the IFR.