Heavy PU poly is slightly better than coated nylons in tropical heavy rains and high winds. There are different types of rain like the monsoon kind which doesn't occur here. Some rains actually hurt your head slightly. With nylons if the pressure of the droplets is strong enough, they might mist as reported by some which will probably be OK in this case as it won't be a sealed tent over night. The pores then snap back like rubber once the immediate pressure is over and misting underneath a little.
Multi tarping might be a good option. A PU poly as the main which will also perform better in high winds not to mention less noisy and a lighter secondary nylon. The nylon can be pitched alongside, slightly overlapping and under, as a shaded porch area and to channel away rain. In heavy rains it can just be snapped underneath the main tarp in case of failure. If using carabiners on one end, you just switch two of them underneath and over to the other side.
Of course if the secondary light nylon tarp is held by carabiners or snap-clips/hooks it can be quickly converted into a side wall to protect against the moving sun, wind, spray, side rain or just needed privacy which is more likely than primary tarp failure. Also the secondary tarp can function as a makeshift shower/loo cubicle. If it is windy, very wet, buggy or needing privacy at night it can become an A framed shelter and with a couple of small pieces of bugnet at each end, it will keep the mossies away too. If the main reason is bugs, it can be pitched tight to the ground and/or slightly buried on the outside if it's a cheap tarp. You can even buy £5 or £10 tarps from DIY superstores for your secondary tarp. Or optionally with a little of the edges folded underneath and loops/grommet holes a few inches from the end. I bought a lightweight tent today but my best buys this week were a large but light retractable pruning saw and £3 waterproof standard blue tarp (9x6) which is not too heavy and some lightweight lines from Homebase as well as 2 lightweight shower curtains in one package for a quick groundsheet/picnic/pack cover etc. from the 99p store which pack to nothing and weigh very little. The DIY stores and Poundland/99p also sell other good stuff like '2' packs of triple LED Stick & Press Lanterns (99p for both) which are great for tents/tarps and are normally £6 quid each! So would be £12 for 2 but in current sales it's BOGOF for £6 in MountainWareHouse stores which is still more than it is at the 99p store which has duct tape and 4-pack paracord, etc.. Poundland's got good stuff too like the multi LED headtorch, the 6-in-1-minitool(whistle, torch, compass, thermo, lens, mirror), etc. MWH BTW is slashing it's sale further by another %20 till Sunday, so I got a £30 quid lightweight pole which was on sale for £17 only for £13.50, some branches have better clothes than others. Also a very nice full tanged carving knife with a great handle for only £2 at Morrisons. I'll be going to Wickes and B&Q next week. Back to topic, so the secondary tarp doesn't have to be an expensive one. Anyway the A framed tarp can just be hung from an existing line or an extension or even a line high at one end and pegged to the ground at other with only one entry which might simplify things even more. Also if it's cheap as groundsheet, or a large beak, gear cover, ... possibilities are endless.
