When using a running martingale with a double bridle, do you put the martingale on the top or bottom rein? I don't want to use a standing martingale but want to have comfort of having a martingale there if I need it!
For the jumping phase you will probably need a hat with a proper harness, so I would suggest go for the GPA - its probably a bit neater than the skull cap if they are anything like mine!
Before you splash out on new boots, why not try putting tubigrip on under your Sabre ones? You can fold this down over the top and put tape round it - this should stop the boots rubbing and save you a few quid too!