I been using a MT 4" double tail split grub most of the time. But I'm thinking for the fall season when the feed bag is on they might not hesitate to strike a longer trailer? If I switch from a 4" trailer to a 6" trailer what do you think? What's the longest trailer you have used so far for spinnerbaits?

To be honest, the only time I use a trailer is in the spring/ pre-spawn.  This time of year, I opt for a short armed single willow blade and the only trailer I use is a trailer hook. I'll also thin out the skirt. 

That said, I would immagine adding a couple of inches to your trailer may make a difference. 

The longest trailer I've ever used was a 6in. swimbait

I only use a trailer in dirty water when I want to bulk up my offering to make it more visible and so I can retrieve it slower. A 5" Grass Pig makes a good trailer with lots of bulk and thump. I've also used pork frogs for trailers. 

Since I have no idea what type of trailer a MT is?? If it''s a standard spinnerbait split tail pencil type trailer going longer doesn't change the overall bulk or profile, just makes it longer. Easy to cut off the longer trailer until the bass react: start with 6" and cut off a 1/2" at a time.

I usually use 4" GY single tail (curl tail) grubs on spinnerbaits year around and change blade sizes and types to change the profile, speed, depth etc.

Tom

Mister Twister 4" split double tail grub

It actually bulks up the spinner bait width wise and looks like it's really alive and swimming. I'm thinking of going longer with a trailer.

MT = Mister Twisted, how did I miss that!

The problem that a twin curl tail grub can cuase an safety pin type spinnerbait bait is the trailer can cuase the roll over. Single tails act as a rudder and help keep the lure run upright.

My recommendation is larger blades if the bait fish are bigger size.

Tom