I am using a moses basket for a bassinet at the moment. I do however have a tall, big baby who I feel will be growing out of this quickly, currently 7 weeks old. I was planning on having her in a cot by the bed as a side car cot. Do you have any information about how to set this up safely? I have measured and there would be a degree of gap between my mattress and her mattress should I look at elevating the cot so it is flush? If I do remove one side of the cot and have it pushed firmly against my mattress, is this safe for her to sleep in as she get bigger and more mobile? Or in this situation would putting the side rail up again be the best thing to do safety wise. Thanks

Red Nose has no information in how to modify a cot.
Product Safety Australia, who develop & monitor Safety Standards in Australia.
They do not recommend modifying cots & have the following information

Product Safety Australia develops & monitors safety standards for products & have this to say on their site.
Infants have died in cots where do-it-yourself repairs have created hazards. If parts of your cot break or stop working, always take it back to the supplier to organise repairs.

Never modify a new or old cot yourself, as this can destroy inbuilt safety features.
https://www.productsafety.gov.au/products/babies-kids/kids-furniture/household-cots

The safest place for baby to sleep, is in a cot that meets mandatory standards on a firm well-fitting & flat mattress in the parents’ room.
https://rednose.org.au/article/what-steps-can-i-take-to-sleep-my-baby-safely

Concerns with side car cot are the risk of entrapment in any gap between cot & adult bed & also falls as baby becomes more mobile.

Red Nose has some information about bassinets which includes.
Falls, injuries and suffocation are the most common risks associated with bassinet use if thebassinet no longer suits the size or developmental needs of the child – once baby is showing signs of being able to roll, it’s time to move to a safe cot.
https://rednose.org.au/article/bassinets