The Guideline for the Compilation of a Mandatory Codes of Practice to Combat Rockfall and Rockburst Accidents (2001) requires regular monitoring of the performance of support systems in important excavations. The guideline for complying with the Mine Support Quality Assurance regulation (14.1.6) (2003) provides recommendations for initial underground testing and underground trialling of elongates followed by evaluation on a regular basis. Although a number of years have lapsed since these documents were published, very few reliable underground load-deformation measurements are available and most support designs are based on generalised derating factors and other adjustments applied to laboratory test results. Recent developments with in-situ load measurement instrumentation have enabled considerably more in-situ performance graphs to be obtained for elongate support units. This paper presents some initial results from these in-situ measurements. The results suggest that commonly held beliefs regarding underground performance and the generalised adjustment factors may not be valid. This conclusion has significant implications for timber support requirements at a time where the supply of timber for mine support is becoming increasingly difficult.