https://www.amazon.com/Gimbal-AE ... bal+cover&psc=1

can I keep this cover on during flight? The add says can be left on, if so great way to protect the gimbal during landings

Well you can fly with the original gimbal cover but you may still get artifacts in your photos and video from any sort of cover.

I say no.  Look closely at your Mavic.  That plastic cover also encloses some air intakes that I'm sure the drone needs for cooling.  The one you are looking at is also curious.  It says that it prevents the gimbal from damage during movement.  But in flight, you NEED that freedom of movement.  
I bought this one:  https://www.amazon.com/gp/produc ... 0?ie=UTF8&psc=1
It serves as both the camera protector bubble, but also has two clips inside that hold the gimbal still when it's on and protects it during travel.  I also stuck some velcro on the side of it and attach a long red ribbon (matching velcro) to remind me that it's on.  

Like 2# mentioned, you can keep the original cover during flying, and it is always the users' preference to fly the drone with or without the gimbal cover. It will protect the camera from the wind to some extent but might also sacrifice the resolution or quality of the pictures and videos in some situations.

The DJI clear plastic cover causes light streaks in the photos.

I bought one of these to protect the lens, yet allow clean photos. problem with this cap, is when I start and stop, the Mavic dips and the top of the hood shows up in the video.

https://www.amazon.com/Mavic-Sha ... RWC1ZZ859JJZ8SNWPQQ

So I just got one of these,

https://www.ebay.com/itm/PGYTECH ... 2060353.m2749.l2649

and am thinking that the upward flair of the hood will solve the issue

I still use the clear plastic one when i pack up the MAVIC in my travel case.

Locoman Posted at 2017-11-7 08:34
The DJI clear plastic cover causes light streaks in the photos.

I bought one of these to protect the lens, yet allow clean photos. problem with this cap, is when I start and stop, the Mavic dips and the top of the hood shows up in the video.

I have this second you bought and it is ok.

I would advise not to - it will restrict airflow through the Mavic during flight and cause flares in the image. If the drone crashes I doubt this will save anything from breaking too. Ideal when in storage/transport to protect the gimbal but not during flight.

the DJI clear cap has a slot cut init to allow for air flow to the internal fan. And allows the camera to do it's initialization. Just remember to remove the little plastic gimbal lock, located behind the camera. The clear one that Sanford got has an internal gimbal lock, so you really should NOT energize the Mavic with that cap installed. As hie said, he needs a reminder to take it off before powering up. I seldom use the camera lock piece.

Thanks for all the responses, I guess one could drill some holes to allow more airflow but for now I will just use the one it came with.

flying with or without the cover only makes a differance to your image quality and especially when turning towards the sun.
Does not affect cooling or create cooling problems - be careful to NOT break or shatter the plexiglass cover if you decide to drill (which i do not advise)