I thought you might be interested in my thoughts.
I've used a variety of ABU multipliers on the cauvery and my choice at present is the ABU Morrum 7700 range, but you would need to acquire them off ebay as they are no longer made. They have a strong body as they are machined from solid aluiminum and very strong, able to take a lot of punishment on the rocks etc. They also hold slightly more line than the very popular 7000 series used an have excellent smooth drags too. I find you can get about 170yds of 40lb big game on a 7000, amrrum adds 30 more yards or so.
The downside consideration is they aren't cheap, they are especaily sort after by US anglers not so over here, so if you see one on sale in the UK it'llbe cheaper. Also, and this is important you should avoid those used in sea fishing as they do corrode with sea water use, especailly if they have not been washed after use. I acquired one like this (a UK source so it was cheap) but it was basically rebuilt internally, runs lovely now.
Although these probs may appear a pain they are cracking reels. I was put onto them by Peter Coogan, who is an expert in servcing ABU reels - and he didn't supply me he's just a very knoweldgable and friendly man to speak if you are looking at ABU ranage. He services John WIlsons reels too, and mentioned JW believes the ABU real cast much better than others. I think JW uses or used the 9000 and 10000 reels on the cauvery.
I also used 10000 for thier extra line capcity (and 9000 which are less so). As mentioned before I have searched for good condition, older (mine are 20+ years old) as these seems to be better then the far east made ones of today.
I started off with new ABU 7000 c3i's which are lovely smooth reels, with a fine drag. However, the real handles are offset quite away from the body of the reall and I feel this can upset the balance of a rod when cranking in. Nut, the biggest issue is with with the handles.
The new big handles really need to be swapped to older smaller handles. This is because the momentum from the large knobs can kick the reel in to gear mid cast. Causing much merriment to those nearby but can knacker the gears. This happened a few time to me, my pal and the guides and took a while to figure out the cause. Not what you want!. Replacing the handle fixes this.
In terms of the level wind, the newer reels seem to suffer from problems. I have had 2 of mine replaced on the ABU 70003ci. the older reels have been fine but to be honest never they seem very substiantail to me. I do have a Morrum without a level wind that I use for lure fishing to maximise casting distance.
However, for me the level wind is very useful to lay the line out nicely and stop diging in. You can get a fair bit of this from snags and catching the odd fish! And as for casting distance, this hasn't posed a problem for me, you rarely cast more than 60 yards, easy with raggi, but distance is more of an issue when using chilwa (live/dead baits) as they have less weight but I don't
think its a real issue in practice.
Some guys I know use and have used for many years, big fixed spool reels and have caught many big fish. As did the mahseer pioneers. However, I've only used them for lure fishing, caught a few (small ones) from the Cauvery and some biggers from the North.
For what is worth I;ve used my old Gt4500 Shimano bait runners but now preferr the 5000 & 10000 XTEA. I have found when lure fishing the thicker line is difficult to control when casting on spinning reels, hence the move to multipliers (although they have there little problems too!). I would say that the spinning reels with instant anti-reverse are a must as my old gt4500 have about half a turn before they engage & stop and this easily allows line to spring off with subsequent birds nests.... I have a great video of a pal of mine trying to disassemble a mighty birds nest.
Blimey, I've gone on a bit here! I hope it is of interest but please note the above is my experience from several visits to India for mahseer but I wouldn't class myself as expert. I've also not had any experience with other manufacturers reels that I have seen in use. My friends, who are seasoned mahseer men used ABU's so seemed senisble to follow suit.
Finally, If you do buy a second hand reel I would recommend getting it serviced & checked before use.
Good luck on the cauvery, have some practice casting beofre you go it'll save some time and fustration later, you'll find the guides will cast for you if you want them to.
BTW, I'm going next year too, can;t wait