Hi all, I'm in definite need of opinions. Thanks in advance. I have a 1/2 size Wilfer ply with a 39.5 string length. Right now it has Helicore hybrid mediums on it and it's flappy and unfocused. The bass has been set up by a really fine luthier. I like pretty low action which is how it's set up. I play primarily jazz and bluegrass, almost always with an amp. The E and A just drop off the map compared to the D and G. I'd be happier with a much higher tension than the heli's. They just don't have any growl or real swell to the tone. Is it possible that because of the shorter string length I should go to a heavier gauge? I don't feel like the heli's are getting the top moving and if I really dig in they wash out. I guess that about covers it. Any suggestions are greatly appreciated.
I should also add that I think the heli's that are on there are 3/4, which probably is even lower tension with a 39.5 string length to begin with.

I think you nailed the problem down with the shorter lenght.
Try to get heavy gauge ones and see the difference.
I don't think the fractionals are available in gauges, only the regulars. (3/4)

Shorter length + lower tension strings + low action = recipe for flabby sound

I'd also reccomend trying heavier gauge strings.

Thanks for confirming the string length issues. Given the above parameters, what would you all recommend for a strings? I realize the subjectivity of your answers, but any suggestions would be great. I think it's going to be possible to get this bass sounding really good, but string choice is going to be the deciding factor at this point. Thanks again.

edit: after remeasuring the bass, the string length is 40 inches, or 101.6 cm. Maybe I could get a high tension 3/4 set?

I would recommend Spirocore Orchestras. You can get them in a 3/4 size. I think you will find them to have a lot more sound than the Helicores.