Snake green gaurd cooking help

You can only eat them when they're young, like a cucumber, after that they turn bitter and tough to eat. I tried it once and never did again 

I eat them as matured like courgette. Scrape the skin with a rub of salt, dice while removing any seeds that are hard and pan fry with oil and then spice it up. Yummm

As in pick them large? Courgette size.
I picked them about 3" long. Fried nothing else still a touch bitter and relatively tasteless.
I was going to add spice later.
What spices would you advise.
And again what length would you advise?
Next year I will have to find a more appropriate place to grow them...like the neighbours garden!
Do they grow happily grow along the ground?

Thanks