Custom/modified Drivetrain 2x/3x Considerations and Planning

I use a modified 26/36/48 crankset on my touring bike. I removed the 26t chainring, as I do not have a use for it. I would ideally pick a 11-32 8-speed cassette, but with the 47cm chainstays a 32-tooth rear and 48-tooth front setup would mean 116-link chain is not long enough. Chains only little longer than 116 links are not available from Shimano (you have to buy 138 link chain then at considerably greater expense than 116 link chain), so I have to accept a 11-30 8-speed cassette. Of course some other chain manufacturer could perhaps sell 118 link chains, but then I cannot use the superior reinforced connecting pin system of Shimano and have to use the horrible quick links that are impossible to disconnect without pliers if the chain is full of dirty sandy oil mixture. Furthermore, having to carry few quick links would mean more extra weight for my emergency tool kit when compared to carrying few reinforced connecting pins, and a portable mini chain tool is necessary anyway. The reinforced connecting pins are also much cheaper than the quick links.

The crankset is actually intended for 9 speeds (it's a Deore Hollowtech II crankset and those are hard to find for 8 speed setups -- I wanted the Hollowtech II feature because the bottom bracket has durable bearings and durable spindle at the same time, being of the outboard type). The rear derailleur is also intended for 9 speeds (it's some old Deore XT). Both of these work just fine in the 8-speed drivetrain. The shift levers are Ultegra 8-speed bar-end shifters. I don't remember what front derailleur I use other than it's intended for double chainring setups. Anyway, the front shifter is of the friction type so the shifter works with all cable pull ratios. Besides, a double front friction shifter is essentially equal to an indexed shifter because the limit stop screws constrain its movement, while at the same time allowing trimming which an indexed shifter system would not allow.

I find that the 36t/30t low gear gets me just fine up very steep hills if I ever encounter one -- most of the time I don't and thus don't need to use the loweest gear I have. At the same time, 48t/17t and 48t/15t allow leisurely flatlands cruising and 48t/13t allows high speeds when I need them. The 48t/11t gear is unused, but if I had the option to switch the 11-30 tooth cassette to 13-30 tooth I wouldn't as I prefer large jumps between gears so that a large change in gear ratio is felt when I operate the shift lever. The 11-30 tooth 8-speed cassette has 15.41% jumps between gears and a hypothetical 13-30 tooth 8-speed cassette would only have 12.69% jumps.

As an added feature, I installed the drivetrain with a full plastic chainguard allowing me to have non-oily trousers after riding the bike, without having to put the end of the right trouser leg inside my sock.

Recently, I have been using an e-road-bike more than the touring bike. The e-road-bike unfortunately has 10-speed drivetrain, but fortunately, the cassette is 11-34 tooth so it still has 13.36% jumps which I can tolerate although I would prefer larger jumps. The drivetrain setup in the e-road-bike is stock as I have not modified it. It doesn't seem to be feasible to install a full chainguard to the e-road-bike so I have to do without.

My preference for lower speeds is caused by lower expense of wearing parts and the observation that it's easier to have big jumps between gears by a lower speed count in the drivetrain. I am aware of a study that found that the higher speed chains are counterintuitively more durable than the lower speed chains due to improved materials despite their narrowness, but my understanding is that the increased durability of these new chains does not offset their higher cost.

In my reading of your question, the big limiting factor is the 29x3. Your question isn't just about what FD/chainring jump hacks function and how well, but also of those which will also work with your clearance needs. The answer to that question is generally not very many, but it's going to depend on the chainstay length of the frame in question, whether the cranks are boost, etc.

Contemporary double MTB FDs of the dainty, short variety that are made to give as much clearance as possible do not play nice with hacking the jump that much. I don't have a ton of experience doing it, which admittedly is what your question is driving at, but if you look at one you'll see that their total top-to-bottom cage space is limited and the contact points for the chain are not large. Maybe you can get it to function okay with 2t extra jump, maybe not.

What always works is just going with a larger cassette range than the total capacity of the RD can handle and accept having a slack chain in some small-small gears. This has been the standby approach to cheating the range on derailleur systems forever and it applies here just the same. Then you're not forever playing games trying to make a front derailleur make a shift it wasn't designed to.

Don't discount just going Rohloff. At 526% the range isn't quite what you're looking for, but obliterating all clearance problems forever is huge.