Sorry, more loft storage questions

[Stuart Farmer]

Hi, I'm after some advice about some storage in our loft. I've added some some photos which hopefully is helpful, or more so than my descriptions! I currently have chipboard floorboards across what I think are rafter ties?? Every rafter tie has a central support fixed to a ceiling joist. Every time I went in the loft over the years I was always told to stay on those particular joists as they would support my weight, they always have, not so sure if they have safely. Anyway, I wanted to sure up the storage as the floorboards span mean they are bowing quite a lot. I wanted to put some 6x2 across the rafter ties and then board over the top. Will they support that additional weight? And any advice about how to go about it? Or could I use loft legs where I've always stood, it's a 5 foot gap between the rafter ties and joists underneath. Thanks for any pointers you can give