Can the upper limit of a lure range on a rod be increased? For instance, if a rod has a lure range of 1/16 oz. to 5/16 oz., is there something I can do to increase the 5/16 to, say 3/8 or 1/2 without affecting the low end of 1/16 or the action? What about an aluminum oversleeve, well secured, and hidden under the rear grip and seat? Would that beef it up just a tad or too much or not at all? I've found the blank I'm looking for as far as the ideal lure range, action, and length but I want to be confident that the rod could handle a little more weight and hall a fish out of dense cover like tree tops.

No, not easily. You can trim a bit off the tip, but it will reduce the lower end of the casting weight range. Most of the casting power is in the upper portion of the rod, so an aluminum sleeve down low isn't going to do what you want, not to mention it will introduce a host of other variables which you aren't likely to want.

Casting requires that you use some means of power adjustment - you wouldn't want to power the rod through a cast with 5/16th ounce as you could do with 1/16 ounce. If you wanted to push the upper limit of the casting weight range, you can do so, provided you exercise some common sense and ease up on the power a bit.

..............

If all your talking about 1/16th of an ounce forget it...There's probably that much variation between any half dozen "5/16" baits.

If what you really need is a rod that will throw baits from 1/16 to 3/8th there are blank out there that are rated for that range.

As far as pulling power is concerned, I recently built a MHX spin-jig rod rated from 1/32 to 1/4.
It was used it to land a 4 pound bass that had to be hauled up a steep 25 foot bank.
I have put together a heavier 3/16 to 5/8 rod for my buddy's wife to use for Northern Pike.
These spin-jig blanks seem to feature a heavy butt section and that's what I think you need for pulling power.
Garry2R's

Garry Thornton Wrote:
-------------------------------------------------------
> If all your talking about 1/16th of an ounce
> forget it...There's probably that much variation
> between any half dozen "5/16" baits.
>
> If what you really need is a rod that will throw
> baits from 1/16 to 3/8th there are blank out there
> that are rated for that range.
>
> As far as pulling power is concerned, I recently
> built a MHX spin-jig rod rated from 1/32 to 1/4.
>
> It was used it to land a 4 pound bass that had to
> be hauled up a steep 25 foot bank.
> I have put together a heavier 3/16 to 5/8 rod for
> my buddy's wife to use for Northern Pike.
> These spin-jig blanks seem to feature a heavy butt
> section and that's what I think you need for
> pulling power.
> Garry2R's


Since Garry brought up the MHX blanks, a quick search shows the SJ841 as having a lure range of 1/16-3/8 ounces. I'm not sure what length you're looking for, but that particular blank works well throughout it's suggested range.
I've never had to wrestle speckled trout or redfish out of a tree but I have had to wrestle them around oyster bars & rocks the size of VW Buses and it's never let me down.