I have put an 11-30 on a short cage Shimano mech with no issues.
Also have a medium cage running a SRAM 11-36 cassette on a Shimano mech with a reversed B-screw. No others mods and changes gear as well as it ever did.
The length of cage lets The mech take up slack in chain so main consideration is differential between the longest the chain has to be (big big) and shortest (small small).
If you have a wide spread on rear like 11-32 and a big gap like 50-34 front then you hit limit of short cage if you use every gear combo (namely big big)
If you have something like 46-36 up front it makes things easier, hence going way over rear cassette size on my CX bike (the 11-36) with no issues.
Likewise if you do not cross the chain to extremes you can get away with a shorter chain length than you might otherwise need and again may be able to use a shorter cage mech
Thanks for the encouragement!
Thanks. Itās SRAM but I am not sure on the cage length. Iāll have to check it out.
Just had exactly this issue with a long weekend in Spain where the main climbs were 3km-8km in length and avg 7-8% grade ā¦ I could spin above 80rpm in sections but my avg was in the 60āsā¦the hire bike was an 11-28 where my home bike is 11-32ā¦I know the options but to be fair the knees were okay so my attitude in the head was focused on āthis will make you strongerāā¦as was quite an odd feelingā¦ lolā¦ at least the lower cadence kept my HR down a bitā¦ 
ā¦ trying to loose weight and retain FTP as go into build phase now as I am sure that will be a faster track to the increased FTP route (240w @ 83kg @ 53yrs old)
I have ridden a lot of hills with various gearing any my own experience has been that my best times have been where I have been able to sustain a cadence close to 80 even on grades over 10%. I solved this with a triple crankset. (Although new 12 speed setups might be just as good) My setup has been 50/40/28 with a 13-30 11 speed cassette. I set a PR of 38:06 on Sa Calobra (Mallorca) with an average cadence of 86, which was about 10% faster than using a compact chainset, with similar results cycling in the alps during la Marmotte - Alpe-dāHuez, Glandon, Galibier. I have done the same rides with a 50/34 + 12-29 and was also grinding at around 50 rpm again with 10% slower total times. Going to a triple is probably not worth the trouble if you donāt regularly cycle steep grades, but do you really need 50/34? There are 46/30 cranks combined with a 11-30 cassette would be almost as good as a triple. You would lose the top end, being restricted to 46-11, but how often do you use 50/11?
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