DPMS 308 Standard length Freefloat tube modification?

[imipenem]

I am in the process of assembling an LR308 from parts.  I am considering the DPMS 308 Standard Length Low 4 Rail Free Float Tube (http://www.dpmsinc.com/308-Standard-Length-Low-4-Rail-Free-Float-Tube_p_324.html).  My barrel is 18" with a mid-length gas system.  There is a note in the handguard description that confuses me it reads - "If you add this to a carbine gas system or a mid length gas system it will need to be modified to be able to set the set screws in the gas block."

My question is why would it have to be modified?  I have assembled 2 ARs with carbine length gas systems and low-pro gas blocks that fit under the handguard and I did not modify them.  I just assembled the gas system before installed the tube/handguard.  Did I do something wrong or is this a pointless disclaimer?

Thanks in advance...

[edgecrusher]

Welcome and I agree with you, that seems to be a strange disclaimer. If it fits under the hand guard, I have no other worries.

[imipenem]

I read it as if they are instructing you to install the handguard FIRST and then install the gas system and tighten the gas block.  But I have not done it that way in the past. 

I just wanted to make sure I was not missing something since this would be my first build using DPMS patterned LR-308 components.

[edgecrusher]

No, in my opinion you are approaching this the right way.

[98Z5V]

All that disclaimer is saying is that there are no holes in the bottom of the handguard.  If you need access to the carbine or midlength-placed gasblock, then you'll need to drill holes in the handguard, in the right places, to access that gasblock.