In this work, we benchmarked concentration sensitivities for spectroscopically orthogonal labelling using dHis-CuNTA in combination with the trityl-based label SLIM at standard Qband (34 GHz) settings in a model protein. We hypothesised that by exchanging the nitroxide MTSL 6 with the trityl SLIM, and by employing the recently introduced variable-time RIDME experiment, distance measurements in the low nanomolar concentration regime should be feasible.