Hey there bt... I understand you wanting to keep your knees safe and spinning... perhaps you try and spin a bit faster?

I use the "step up" routine outlined in the book "The Female Cyclist" to improve my cadence and that lifts my HR slightly...

You say your HR sky-rockets whilst running... I know that sometimes mine feels like it is but when I check my monitor it is 20 or so beats below where I think it is. Having a heart rate monitor is one useful tool in your training repertoirre, so def put one on your wish-list... but it is just one tool of many.

If you know where your estimated LT is, then work with that and aim to exert yourself to an extent where you place yourself near this zone that you recognise from your running.

If you do find you love TTs, then gradually keep working at increasing the gears but keep spinning them... sometimes you go faster by changing down the gear and spinning, than by changing up and grinding.

Glad the aero-bars are feeling more comfortable