In my hands, no.
The reason is when you lay the flask on its side during incubation, the amount of media flows too closely to the neck which could lead to contamination.
For suspension cultures, the largest volume I've used is 16 mL.
If you need larger volume, try a spinner flask or roller bottle.
yes your are correct i used only 15ml but i saw that we can make upto 40ml
i want to try...as it is not possible to keep the flask flat ...could it be possible to stand the flask ?
do the cells still be happy in that conditions with less length?
I don't think your cell will be happy.
If you stand the flask, the cell will accumulate at the bottom of the flask and reduce the area for them to grow.
The cells at the very bottom will not get nutrient from the medium. Unless you gently shake the flask every hour.
This is why people invented rolling bottle.
Hope this may help.