If you want to avoid carrying ultra fast films such as Delta 3200 and TMZ because of the risk of X-ray fog I'd recommend something like TMY at EI 800-1600 in Microphen.

Use the developer as stock solution, straight up, no rocks, no chaser. I see finer grain, better gradation and a more effective speed boost this way than with any dilution. The used developer can be reused several times this way. I reuse a liter 10 times this way.

Shadow detail will be somewhat inferior to Delta 3200 but in my results grain is finer and midtone gradation smoother with pushed TMY. And there should be less risk of fog from airport X-rays.