Min/Max Month on Month Change Not Working To Get Values

[itcapability]

I have 2 charts, a monthly average chart and a monthly "delta" chart (see table as example).  The formula used are:

Dimension: [Test Date.autoCalendar.YearMonth]

Measure 1: avg({<ISP={"V*"},[Test Date.autoCalendar.MonthsAgo]={">=1<=6"},[Speed]={">0<=80"}>} [Speed])

Measure 2: avg({<ISP={"V*"},[Test Date.autoCalendar.MonthsAgo]={">=1<=6"},[Speed]={">0<=80"}>} [Speed])
  -above(avg({<ISP={"V*"},[Test Date.autoCalendar.MonthsAgo]={">=1<=6"},[Speed]={">0<=80"}>} [Speed]))

Test Date.YearMonth	Monthly Average	Monthly Delta
2019-Jul	28.72	-
2019-Aug	27.20	-1.52
2019-Sep	30.15	2.95
2019-Oct	31.16	1.01
2019-Nov	31.23	0.07
2019-Dec	31.04	-0.19

These 2 formula work fine in a chart or table. I am now trying to find the minimum and maximum values (red and blue in the table above).  I have wrapped Measure 2 with max(aggr()) in various ways and either get a "cannot have nested aggregation" error, no value or the wrong value (2.5, 13, 63, 71).

I'm not sure what I need to do know. Any help ??

Regards,

Adrian