Matching with pythia decays

I would like to produce matched events with extra jets produced at the matrix element level.

However, I also need a reasonably long decay chain and if I attempt this in Madgraph the calculation time is too long.

Therefore I am attempting to do the decays within pythia.

However, with this setup, I find that almost no events survive the matching procedure and I was wondering if there is a solution?

Many thanks,
Jamie