1. At JET successful measures are taken to delay the outer modes and to improve performance. 2. In accord with theoretical predictions, observations show that ramping down l_p delays the outer mode. 3. Improvements in the neutron yield of 45 % have been obtained. 4. However, the improvement in performance which can be achieved by delaying the outer mode is eventually halted by an earlier onset of a giant ELM 5.MHD observations at different values of l_p, confirm the interpretation of outer modes as external kinks, while indicating that the giant ELMs occur as the ballooning limit is approached. 6. The effect of gas bleeding on the edge MHD stability has been studied. For the levels of gas routinely used, no significant improvement in either kink or ballooning stability is expected. 7. Further increase in the edge density, would cool the plasma edge, delaying both ballooning and external kink modes, however performance would not improve due to the increased heat losses. 8. Observations show that gas bleed is an effective way to reduce Z_(eff).
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