I mounted my speeder bikes with an acrylic rod with a ball bearing to make it pose able. I did measure out the stock base and size the rid with bearing to the same size and marked the front facing firing arc. Would this be a problem in organised play?

It depends on the level of the event you are participating in. In all cases, you will have to check with the TO of the specific event

What about this type of mod. They are 3d printed parts to add on

9 minutes ago, irav222 said:

What about this type of mod. They are 3d printed parts to add on

As before, it really comes down to what level of tournament and how strict the TO is on enforcement.

Those parts may be determined to "significantly alter the shape of the model." I recommend you read over the Tournament Rules , read any individual tournament packets, and contact the TO of any tournaments you wish to participate in prior to the event as to whether your modifications would be allowed.

I dont think a slightly altered flying stand doesn't significantly alter the model

This is a hobby wargame if you can't do some slight custom base work it is failing in its basic aim.