Will the plants be too tall for the tent?

600w Dual Spectrum
24/0 Cycle
10 gallon Smartpots
In veg for a month and now are 9'' tall
Top height of the light in a tent is 6'
I intend to top them two times and veg them for month and a half more,thats 2 and a half months all together before putting them in 12/12 cycle
Will they grow too big for me?

No one will be able to give an accurate guess without knowing the strain and the genetics. For example if the strain was mostly sativa such as kali mist you would probably run into problems but for an indica or hybrid you might be ok.

Super Silver Haze (Sativa) And Jack Herer (Indica)
But they height is similar at end SSH is only faster growing strain

What you need to do is find the amount vertical space you have to work with. The easiest way to do this would be to do the following: put your light as high as it can go and measure from the top of your grow pot to the top of the light(remember or write this number down); Find out how close you can keep your light from the canopy to maintain acceptable temperatures( this will vary depending on your reflector and air circulation); Now subtract the distance from the second step from the first.

Total Height from top of pot - distance between the light and canopy = Total useable vertical space

From here you will have to find out how much the plants like to stretch in flower. Once you find that percentage you just divide the total useable vertical space by it. So lets say the plant is known to generally double in size or increase by 200% it would be
totalSpace/2.
Total useable vertical space / expected stretch = Height you can grow your plants to

I would think It is always wise in these type of situations to leave some room for the unexpected unless you are familiar with the genetics and have mastered the plants growth traits. As every ones variables are different there is no definite way to say if the plants will be too big in your intended veg time however I hope this provides you with how to figure it out according to your environment and space.

Hope this was helpful.